Get Air conditioning system -> 2 Working with air conditioner service station Guide for Volkswagen Touran 4 Door Second Generation (2015-2022)

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

Note

♦ Replacement compressors contain a certain specified quantity

of refrigerant oil. On vehicles with two evaporators, a certain

amount of refrigerant oil may also have to be filled in the circuit

if necessary ⇒ Heating, air conditioning; Rep. gr. 00 ; Tech‐

nical data and ⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerant circuit; System overview - refrigerant circuit .

♦ If the air conditioner compressor does not need to be renewed,

replenish the refrigerant oil accordingly up to the prescribed fill

level (empty refrigerant oil and pour the prescribed volume

back into the air conditioner compressor or refrigerant circuit)

⇒ page 79 , ⇒ Heating, air conditioning; Rep. gr. 00 ; Tech‐

nical data; refrigerant oil .

– Completely reassemble the refrigerant circuit again ⇒ Heat‐

ing, air conditioning; Rep. gr. 87 ; Refrigerant circuit; System

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overview - refrigerant circuit (vehicle-specific workshop man‐

ual).

– Evacuate and charge the refrigerant circuit in the prescribed

manner ⇒ “2.5 Evacuating refrigerant circuit”, page 140 and

⇒ “2.6 Charging refrigerant circuit”, page 146

– Bring the air conditioning system into operation in the prescri‐

bed manner ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrig‐

erant circuit; Bringing air conditioning system into operation

after charging refrigerant circuit and

⇒ “2.7 Bringing air conditioning system into service after

charging”, page 149

1. Refrigerant circuit

125

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1.7

Checking pressures with pressure

gauge

⇒ “1.7.1 Display on pressure gauges”, page 126

⇒ “1.7.2 Pressure gauges enable the following test and meas‐

urement work”, page 126

1.7.1

Display on pressure gauges

1 - Temperature scale for R1234yf refrigerant (CF CF = CH )

3

2

in °C

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2 - Pressure scale in bar overpressure

Note

♦ Pressure is indicated in various units: 1 MPa (Mega-Pascal)

is equal to 10 bar or 145 psi; 1 bar absolute pressure is equal

to 0 bar, which is about the same as ambient pressure (at‐

mospheric pressure).

♦ This diagram shows a pressure gauge displaying pressure on

the low pressure side. The display here is shown in bar over‐

pressure (noticeable by “-1” in the display).

In addition to the pressure scale, the pressure gauges can have

one or more temperature scales. The scale values for R1234yf

are assigned according to the vapour pressure table. Because

different refrigerants have different vapour pressures at the same

temperature, each temperature scale is labelled for the respective

refrigerant.

♦ Pressure gauges enable the following testing and measuring

measures

⇒ “1.7.2 Pressure gauges enable the following test and meas‐

urement work”, page 126 .

1.7.2

Pressure gauges enable the following

test and measurement work

Pressure and temperature measurement in refrigerant circuit

♦ The high pressure gauge allows the pressure (and tempera‐

ture) to be measured with the air conditioning system switched

on irrespective of whether this is at the outlet of the air condi‐

tioner compressor through the condenser up to the restriction

(restrictor or expansion valve).

♦ The low pressure gauge facilitates measurement of the pres‐

sure (and temperature) that spreads evenly from the restric‐

tion (restrictor or expansion valve) through the evaporator up

to the inlet of the air conditioner compressor with the air con‐

ditioning system switched on.

Note

The relationship between pressure and temperature shown on

the pressure gauges is valid only where the refrigerant in the cir‐

cuit is liquid or vapour, but not when it is gas. In the gaseous state,

the temperature is approx. 10°C to 30°C higher than indicated on

the pressure gauge.

Evidence of refrigerant in a closed container

R1234yf refrigerant is present in a closed container or refrigerant

circuit if the temperature indicated on the pressure gauge corre‐

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

sponds to the temperature of the refrigerant (the temperature of

a standing fluid stabilises at ambient temperature).

A closed container or isolated refrigerant circuit is empty if the

temperature indicated on the pressure gauge is below the tem‐

perature of the refrigerant.

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Note

♦ The dependency between pressure and temperature descri‐

bed on the pressure gauges no longer applies when there is

no liquid and the pressure is created by gas alone.

♦ Since the R1234yf and R134a refrigerant pressures are very

close to each other over a broad temperature range, it is not

possible to distinguish between them by means of the pres‐

sure measurement. It is possible to distinguish between them

e.g. by means of a gas analysis

⇒ “6.2.16 Analysis of refrigerant R1234yf”, page 24 .

1. Refrigerant circuit

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128

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

2

Working with air conditioner service

station

⇒ “2.1 Working with air conditioner service station”, page 129

⇒ “2.2 Connecting air conditioner service station to refrigerant ^lk

circuit”, page 131

⇒ “2.3 Performing gas analysis of refrigerant”, page 134

⇒ “2.4 Emptying refrigerant circuit”, page 137

⇒ “2.5 Evacuating refrigerant circuit”, page 140

⇒ “2.6 Charging refrigerant circuit”, page 146

⇒ “2.7 Bringing air conditioning system into service after charg‐

ing”, page 149

⇒ “2.8 Switching off air conditioner service station and separating

from refrigerant circuit”, page 151

⇒ “2.9 Charging refrigerant in reservoir”, page 153

⇒ “2.10 Emptying air conditioner service station”, page 154

⇒ “2.11 Cleaning electrical air conditioning compressor”,

page 155

⇒ “2.12 Cleaning refrigerant circuit”, page 157

⇒ “2.13 Filling contaminated refrigerant in a recycling cylinder for

analysis, processing or disposal”, page 161

⇒ “2.14 Checking pressures”, page 170

2.1

Working with air conditioner service sta‐

tion

Note

♦ Should there be any reason to believe that chemical substan‐

ces (leak stop additives) have been used to seal leaks in the

refrigerant circuit from which refrigerant is to be extracted, do

not connect the air conditioner service station to this refriger‐

ant circuit and do not extract the refrigerant.

♦ Chemical substances used to seal leaks form deposits in the

refrigerant circuit. These can impair the function of the air con‐

ditioning system and cause the air conditioning system (and

your air conditioner service station ) to fail.

♦ Bring the customer's attention to the presence of substances

in the air conditioning system that are not approved by Volks‐

wagen/Audi, which prevent the air conditioning system from

being flushed and repaired.

♦ Volkswagen/Audi does not authorise the use of chemical sub‐

stances (leak stop additives) for purposes of sealing leaks in

refrigerant circuits. There are currently no long-term tests, ef‐

fectiveness or material-compatibility tests. As such, there is no

way of ruling out damage or malfunctions in an air conditioning

system or air conditioner service station .

♦ The leak stop additives currently available on the market have

different physical and chemical properties. These could impair

the function of the air conditioning system and air conditioner

service station with lasting effect or even cause a total failure.

VW/Volkswagen/Audi does not endorse the use of chemical

substances (leak inhibitor additives) for purposes of sealing

leaks in refrigerant circuits.

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

♦ These chemical substances (leak stop additives) react mostly

with the ambient air or the humidity to stop leaks in the refrig‐

erant circuit. They cause deposits to build up in the refrigerant

circuit (and your air conditioner service station ), cause valves

to malfunction and defects in other components with which

they come into contact. These deposits cannot be completely

removed from the components (not even by flushing).

♦ There are often no external signs to suggest that chemical

substances (leak stop additives) have been used to seal leaks

in a refrigerant circuit. Often, the stickers that are meant to be

used to mark such systems are missing. Therefore, exercise

caution on vehicles for which you have no service or repair

record.

♦ Containers or tanks with integrated filters are offered as ac‐

cessories on the open market that are designed to separate

these chemical substances (leak stop additives for sealing

leaks). Since Volkswagen/Audi is unaware of the composition

and the physical and chemical properties of these substances,

no statement can be made at this point as to the effectiveness

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and the filtering capability of these filters.

If repair work needs to be carried out on the refrigerant circuit of

the air conditioning system on a vehicle whose refrigerant circuit

has been filled with chemical substances (leak stop additives) to

seal leaking components (or there is good reason to believe that

this has been the case), bring the client's (the vehicle owner's)

attention to the following situation:

♦ The refrigerant of the air conditioning system cannot be ex‐

tracted owing to the substances (leak stop additives) that it

contains, which can damage your air conditioner service sta‐

tion . To extract the refrigerant, it can be filled in a recycling

cylinder in the way described for contaminated refrigerant

⇒ “2.13 Filling contaminated refrigerant in a recycling cylinder

for analysis, processing or disposal”, page 161 . Should this

not be possible, it may be necessary e.g. for a company to be

entrusted with extraction of the contaminated refrigerant using

a suitable device. This should then be processed (or disposed

of) e.g. by a local disposal company well versed in the proce‐

dures relating to the disposal of refrigerants.

♦ For proper repair of the air conditioning system, it is necessary

to renew all components of the refrigerant circuit that have

come into contact with the leak stop additive. The leak stop

additive could already have damaged some components of

the refrigerant circuit (e.g. the air conditioner compressor reg‐

ulating valve - N280- ) or subsequently cause damage when

the system is brought back into operation and, after a short

time, failure of said components. Furthermore, deposits of leak

stop additive in the components of the refrigerant circuit may

work loose at a later stage, leading to renewed failure of the

air conditioning system (completely cleaning these compo‐

nents using workshop equipment is currently not possible).

♦ Contaminated refrigerant can render the whole filling in your

air conditioner service station unusable.

♦ Before extracting with a suitable tester, check the composition

of the refrigerant in the refrigerant circuit

⇒ “2.3 Performing gas analysis of refrigerant”, page 134 .

♦ Extract contaminated refrigerant into a recycling cylinder and

send this in to your gas supplier for analysis, processing or

disposal

⇒ “6.2.17 Returning contaminated R1234yf refrigerant for

analysis, processing or disposal”, page 25 .

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Note

♦ Contaminated refrigerant can change the way in which the air

conditioning system works and / or permanently damage com‐

ponents of the refrigerant circuit.

♦ Mixtures of different refrigerants (e.g. R1234yf refrigerant with

an unknown quantity of R134a refrigerant) may not be filled in

a vehicle that has been given type approval for R1234yf re‐

frigerant.

Important instructions for working with air conditioner service sta‐

tion

To operate the air conditioner service station ( air conditioner

service station currently available ⇒ Workshop equipment and

special tools catalogue ), the following must be observed:

lk

♦ The fitted filter and dryer must be renewed at the latest when

the operational time specified in the related operating instruc‐

tions has been reached.

♦ If an air conditioner service station is also used to clean (flush)

the refrigerant circuit, the dryer and filter installed in the system

must be replaced at shorter intervals ⇒ page 124 .

♦ Only refrigerant oils that are approved for the vehicle-specific

refrigerant circuit may be filled in the reservoir (pour the re‐

frigerant oil directly into the refrigerant circuit if necessary) ⇒

Electronic parts catalogue .

♦ Depending on the version of air conditioner service station and

the measures to be performed, there is a minimum volume of

refrigerant, refrigerant oil and UV leak detection additive that

must be in the respective supply reservoirs of the air condi‐

tioner service station ⇒ Operating instructions air conditioner

service station

In the event of any doubt regarding the composition of the refrig‐

erant extracted from the refrigerant circuit, the extracted refriger‐

ant must not be re-used even after it has been cleaned in the air

conditioner service station

⇒ “2.3 Performing gas analysis of refrigerant”, page 134 .

♦ If the wrong refrigerant has been accidentally poured in the air

conditioner service station , it must be emptied

⇒ “2.4 Emptying refrigerant circuit”, page 137 and

⇒ “2.2 Connecting air conditioner service station to refrigerant

circuit”, page 131 . The system may also need to be cleaned,

including renewal of the filters, dryers and refrigerant oil.

♦ Contaminated refrigerant, e.g. in Germany, can be returned to

the supplier in so-called recycling cylinders for analysis, pro‐

cessing or environmentally-compatible disposal (in other

countries, different or additional regulations may apply)

⇒ “6.2.17 Returning contaminated R1234yf refrigerant for

analysis, processing or disposal”, page 25 .

2.2

Connecting air conditioner service sta‐

tion to refrigerant circuit

Connecting

•

Depending on the type of equipment chosen, there may be

variations in the required procedure; therefore always follow

the user's manual for the equipment being used.

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Note

The procedure described in the instruction manual for your air

conditioning service station is to be followed ⇒ Operating instruc‐

tions air conditioner service station .

The charging hoses must only be connected according to the fol‐

lowing work procedure to prevent air or moisture from entering

the refrigerant circuit:

– On vehicles with high-voltage system, switch off “stationary air

conditioning” function (deactivate)⇒ Owner's Manual and ⇒

Operating instructions of infotainment / MMI .

– Switch off ignition.

– Connect the air conditioner service station to the power sup‐

ply.

– Switch on the air conditioner service station and bring it into

operation as described in the instructions ⇒ Operating in‐

structions air conditioner service station .

lk

– Unscrew the sealing caps from the service connections (see

vehicle-specific refrigerant circuit) ⇒ Heating, air conditioning;

Rep. gr. 87 ; Refrigerant circuit (vehicle-specific workshop

manual).

– Evacuate the charge hoses if necessary.

– Check service connections of refrigerant circuit for contami‐

nation or corrosion, clean if necessary.

Note

Dirt or a rough surface on the service connections caused by cor‐

rosion can cause damage to the seals and thereby premature

failure of the quick-release couplings.

– Fit quick-release couplings to the service connections of the

refrigerant circuit.

NOTICE

Risk of damage to the air conditioner compressor or air condi‐

tioner service station.

Opening the valves with the air conditioning system switched

on can cause a short circuit between the high pressure and low

pressure side.

– Never open valves on the high pressure or low pressure side

with the air conditioning system switched on.

– Turn the handwheel of the quick-release coupling adapter on

the low pressure side no further than necessary to completely

open the service connection (observe pressure gauge; do not

over-tighten valve).

– Perform a gas analysis using the air conditioner service station

(only necessary if refrigerant needs to be extracted or pres‐

sures in the refrigerant circuit need to be checked)

⇒ “2.3 Performing gas analysis of refrigerant”, page 134 .

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Note

Connect the gas analysis device or air conditioner service station

to the refrigerant circuit as instructed to do so, and bring it into

operation ⇒ Operating instructions of gas analysis device ,

⇒ page 131 and / or ⇒ Operating instructions air conditioner

service station .

lk

If during the gas analysis it is found that the refrigerant in the cir‐

cuit meets the specifications:

– Turn the handwheel of the quick-release coupling adapter on

the high pressure side no further than necessary to completely

open the service connection (observe pressure gauge; do not

over-tighten valve).

– Perform the measures as required on the refrigerant circuit

using the air conditioner service station .

Note

♦ If, during the gas analysis, it is found that the R1234y refrig‐

erant is contaminated, extract the refrigerant from the refrig‐

erant circuit and send it back e.g. to your gas supplier for

processing (or disposal)

⇒ “2.13 Filling contaminated refrigerant in a recycling cylinder

for analysis, processing or disposal”, page 161 ,

⇒ “6.2.17 Returning contaminated R1234yf refrigerant for

analysis, processing or disposal”, page 25 and

⇒ “6.1 Basics of air conditioning technology”, page 16 .

♦ Should there be no means of doing this, extract the contami‐

nated refrigerant immediately from the refrigerant circuit of the

vehicle and collect in a recycling cylinder. Unscrew (close) the

handwheel of the quick release coupling adapter on the low

pressure side, switch off the air conditioner service station

(and isolate from the power supply if necessary). Then sepa‐

rate the quick release coupling adapter on the low pressure

side from the vehicle. The quick release coupling adapter on

the low pressure side must then be separated - e.g. with a

suction hose from the workshop extraction unit - from the

charge hose for the air conditioner service station and the

contaminated refrigerant allowed to flow out of the charge

hose into the extraction hose of the workshop extraction unit.

To restore operational readiness of the air conditioner service

station , reinstall the quick release coupling adapter on the low

pressure side on the charge hose for the air conditioner serv‐

ice station and evacuate using the air conditioner service

station as instructed to do so in the relevant operating instruc‐

tions ⇒ Operating instructions air conditioner service station .

– Perform the measures as required using the air conditioner

service station .

♦ ⇒ “2.3 Performing gas analysis of refrigerant”, page 134

♦ ⇒ “2.4 Emptying refrigerant circuit”, page 137 .

♦ ⇒ “2.5 Evacuating refrigerant circuit”, page 140 .

♦ ⇒ “2.6 Charging refrigerant circuit”, page 146 .

♦ ⇒ “2.8 Switching off air conditioner service station and sepa‐

rating from refrigerant circuit”, page 151

♦ ⇒ “2.9 Charging refrigerant in reservoir”, page 153 .

♦ ⇒ “2.10 Emptying air conditioner service station”, page 154 .

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♦ ⇒ “2.14 Checking pressures”, page 170

2.3

Performing gas analysis of refrigerant

Note

♦ For operation of the air conditioning system, it is important that

the refrigerant used has a certain degree of purity.

♦ Contamination with other refrigerants or gases can cause

damage and thereby failure of the air conditioning system.

♦ Contaminated refrigerant must be returned as gas of unknown

composition e.g. to your gas supplier for processing (or dis‐

posal) in accordance with legislative requirements ⇒ VW /

Audi-ServiceNet .

♦ To prevent liquid components (e.g. droplets of refrigerant oil)

in the extracted refrigerant gas from falsifying the result of the

gas analysis, separators (filters) are installed in the gas anal‐

ysis device that separate these droplets of liquid. Renew

separators in accordance with specifications of gas analysis

device or operating instructions of air conditioner service sta‐

tion ⇒ Operating instructions of gas analysis device or ⇒

Operating instructions of air conditioner service station .

All vehicles

– Connect the gas analysis device or air conditioner service sta‐

tion to the refrigerant circuit as instructed to do so, and bring

it into operation ⇒ Operating instructions of gas analysis de‐

vice ,

⇒ “2.2 Connecting air conditioner service station to refrigerant

circuit”, page 131 and / or ⇒ Operating instructions air condi‐

tioner service station .

lk

– Perform the gas analysis as per the operating instructions.

Note

♦ A faulty gas analysis is possible from air in the refrigerant ho‐

ses or non-observance of the procedure for gas analysis as

detailed in the operating instructions.

♦ Carefully follow the operating instructions of the gas analysis

device / air conditioner service station .

♦ Evacuate refrigerant hoses of the air conditioner service sta‐

tion before connecting the service couplings to the refrigerant

circuit / gas cylinder with R1234yf refrigerant hose (see oper‐

ating instructions of gas analysis device / air conditioner serv‐

ice station

⇒ “2.3 Performing gas analysis of refrigerant”, page 134 .

The gas analysis may provide the following results:

♦ The R1234yf refrigerant complies with the specifications, the

planned measures may be performed with the air conditioner

service station .

♦ A fault occurred during the gas analysis. The fault is to be in‐

vestigated and rectified after which the gas analysis must be

repeated.

♦ The analysed R1234yf refrigerant does not comply with the

specifications, the analysed refrigerant must be extracted as

refrigerant of unknown composition and returned e.g. to your

gas supplier for processing (or disposal)

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⇒ “6.2.17 Returning contaminated R1234yf refrigerant for

analysis, processing or disposal”, page 25

Note

♦ Should the analysis of the refrigerant - to be extracted e.g. from

the refrigerant circuit of a vehicle - indicate that it is contami‐

nated: you can also perform a gas analysis on the refrigerant

e.g. of another cylinder from your gas supplier if you wish to

verify the analysis result.

♦ Since R1234yf refrigerant is so pure, even small amounts of

ambient air in the charge hoses of the air conditioner service

station can falsify the results. For this reason, most air condi‐

tioner service stations have a feature via which the gas anal‐

ysis is repeated up to 2 times before a not OK result is

displayed ⇒ Operating manual for air conditioner service sta‐

tion .

♦ You can perform a simple function check on your gas analysis

device e.g. using ambient air (unscrew the service coupling

from the refrigerant hose with which the gas analysis is per‐

formed and analyse the gas with the refrigerant hose open).

The result of this test should then indicate that the analysed

gas is not OK.

♦ The method of gas analysis employed here was developed for

motor vehicle workshops. It provides no details about the pre‐

cise composition of the refrigerant. This gas analysis can

therefore only show how high the percentage of R1234yf re‐

frigerant is in the refrigerant analysed. If the percentage of

R1234yf is below 95%, the refrigerant does not comply with

the specifications and can cause damage to the components

of the refrigerant circuit. A gas analysis that also provides de‐

tails about the precise composition of the analysed refrigerant

is currently not available for workshops. Gas analyses with

which the precise composition of gases can be investigated

require complicated equipment and procedures and can usu‐

ally only be performed with dedicated testing facilities.

Should contaminated refrigerant be found during the gas analy‐

sis, notify the customer before continuing work and bring the

customer's attention to the following:

There is contaminated refrigerant or refrigerant of unknown com‐

position in the refrigerant circuit of his vehicle that does not

comply with the vehicle manufacturer's specifications. This re‐

frigerant:

♦ must be returned e.g. to the gas supplier as refrigerant of un‐

known composition for analysis, processing (or disposal)

⇒ “6.2.17 Returning contaminated R1234yf refrigerant for

analysis, processing or disposal”, page 25 .

♦ can be the cause of a malfunction or may already have caused

damage that makes the inevitability of malfunctions in the near

future probable.

♦ Depending on its composition, the use of contaminated refrig‐

erant could lead to the operating permit of the vehicle being

withdrawn.

♦ If, as a result of contaminated refrigerant, internal damage to

the refrigerant circuit has been caused (e.g. decomposition

products of the contaminated refrigerant have affected the

components of the refrigerant circuit

⇒ “1.5 Renewing components”, page 79 ), the refrigerant cir‐

cuit can only be restored to full functionality once all compo‐

nents that came into contact with the contaminated refrigerant

have been renewed. The internal condition of the refrigerant

circuit can be appraised e.g. by visually inspecting certain

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components of the refrigerant circuit (e.g. the condition of the

internal surfaces of removed refrigerant lines and refrigerant

hoses, the internal surface of the refrigerant reservoir and the

condition of the removed dryer cartridge).

♦ If internal damage has been caused to the refrigerant circuit

through contaminated refrigerant (e.g. failure of the air condi‐

tioner compressor has ensued owing to damaged control

elements or overheating, refrigerant oil has a stronger colour

than usual but the parts containing refrigerant have not been

affected ⇒ “1.5 Renewing components”, page 79 ), the refrig‐

erant circuit can be charged again once it has been flushed

(renew air conditioner compressor, dryer and expansion

valve). However, since there is no way of anticipating the long-

term effect of the contaminated refrigerant on the refrigerant

oil and the components of the refrigerant circuit, no guarantee

can be given in this case that the components of the refrigerant

circuit will function correctly in future.

♦ If the contaminated refrigerant has not caused internal dam‐

age to the refrigerant circuit (e.g. the refrigerant oil does not

have a stronger colour than usual, the components of the re‐

frigerant circuit have not been affected), the refrigerant circuit

can be charged again once the dryer has been renewed and

the refrigerant circuit has been evacuated for an extended pe‐

riod (at least 1 hour). However, since there is no way of

lk

anticipating the long-term effect of the contaminated refriger‐

ant on the refrigerant oil and the components of the refrigerant

circuit, no guarantee can be given in this case that the com‐

ponents of the refrigerant circuit will function correctly in future

⇒ “1.5 Renewing components”, page 79 .

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Note

♦ If there is a complaint that can be attributed to the contamina‐

ted refrigerant (e.g. leaking seals or hoses, damage to the air

conditioner compressor, contaminated refrigerant oil), the re‐

frigerant circuit must be flushed and then all components that

were damaged by the contaminated refrigerant (seals, hoses,

reservoir or dryer cartridge, expansion valve and air condi‐

tioner compressor) must be renewed. If it is found that the

contaminated refrigerant has affected other components as

well (e.g. the internal surfaces of the refrigerant pipes and re‐

frigerant hoses, damaged seals), the complete refrigerant cir‐

cuit must be renewed. The refrigerant circuit must then be

recharged with clean refrigerant. Then check the function of

the air conditioning system. For the customer and to safeguard

yourself, make a note that the refrigerant circuit was charged

with contaminated refrigerant.

♦ If there is a complaint that can be attributed to the contamina‐

lk

ted refrigerant (e.g. loss or lack of cooling output) and no other

complaints can be found in the refrigerant circuit, or if the re‐

frigerant has to be extracted because work in the area of the

refrigerant circuit so requires, proceed as follows after evacu‐

ating the system. Remove the dryer and check for contami‐

nation. Since there could also be refrigerant oil on or in the

dryer, check this as well. If the refrigerant oil is contaminated,

dark or viscous or if deposits of dirt have built-up on the dryer,

flush the refrigerant circuit and renew the parts as described

above (damage may already have been caused, which could

soon lead to failure of the air conditioning system). If the re‐

frigerant oil is OK and the dryer is not contaminated any more

than is usual from normal operation, renew the dryer. Evacu‐

ate the refrigerant circuit for an extended period (at least 1

hour) and then recharge with clean refrigerant. Check the

function of the air conditioning system. For the customer and

to safeguard yourself, make a note that the refrigerant circuit

was charged with contaminated refrigerant.

2.4

Emptying refrigerant circuit

•

Depending on the type of equipment chosen, there may be

changes to the procedure (always follow user's manual for the

equipment being used) ⇒ Operating instructions air condi‐

tioner service station .

•

The refrigerant circuit should be emptied if parts of the refrig‐

erant circuit are to be removed, if it is unclear whether there is

refrigerant in the circuit, if contaminated refrigerant was de‐

termined during the gas analysis, or if safety precautions so

demand.

•

All of the operating instructions for work involving refrigerant

with the air conditioner service station can be found in the op‐

erating instructions of the air conditioner service station ⇒

Operating instructions air conditioner service station .

Draining

– On vehicles with high-voltage system, switch off “stationary air

conditioning” function (deactivate)⇒ Owner's Manual .

– Switch off ignition.

– Connect the air conditioner service station to the power sup‐

ply.

In addition for vehicles with electrically-actuated valves in the re‐

frigerant circuit that are not open when de-energised:

2. Working with air conditioner service station

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On vehicles with high-voltage system and auxiliary air condition‐

ing system functions (“heat pump mode” or “cooling of high-

voltage battery”), valves may be installed in the refrigerant circuit

that are not open when de-energised. These valves are opened

and closed e.g. via incremental motors and are no longer actu‐

ated when the ignition is switched off. To empty completely, for

correct evacuation and charging of the refrigerant circuit, howev‐

er, no areas may be isolated, which is why these valves must be

opened before work is carried out ⇒ Heating, air conditioning;

Rep. gr. 87 ; Refrigerant circuit; System overview - refrigerant

circuit and ⇒ Vehicle diagnostic tester in “Guided Fault Finding”

mode.

– Using ⇒ Vehicle diagnostic tester, open any valves which are

not open in their resting state.

All vehicles

– Bring the air conditioner service station into operation as in‐

structed in the associated operating manual.

– Unscrew the sealing caps from the service connections of the

refrigerant circuit (see vehicle-specific refrigerant circuit) ⇒

Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit;

System overview - refrigerant circuit .

– Connect air conditioner service station to refrigerant circuit

⇒ “2.2 Connecting air conditioner service station to refrigerant

circuit”, page 131 .

– Perform a gas analysis with the air conditioner service station

⇒ “2.3 Performing gas analysis of refrigerant”, page 134 .

Note

lk

♦ If during the gas analysis it is found that the R1234y refrigerant

is contaminated, extract the refrigerant from the refrigerant

circuit and send it e.g. back to your gas supplier for analysis,

processing or disposal

⇒ “6.2.17 Returning contaminated R1234yf refrigerant for

analysis, processing or disposal”, page 25 .

♦ Refill the refrigerant that is contaminated into a recycling cyl‐

inder and return it e.g. to your gas supplier for analysis, pro‐

cessing or disposal

⇒ “6.2.17 Returning contaminated R1234yf refrigerant for

analysis, processing or disposal”, page 25 .

– Evacuate the refrigerant circuit with the air conditioner service

station as instructed in the associated operating manual.

NOTICE

Risk of damage to air conditioner compressor if refrigerant cir‐

cuit is empty.

– Never start the engine if the refrigerant circuit is empty.

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Note

♦ Sometimes, refrigerant oil is extracted from the refrigerant cir‐

cuit along with the refrigerant and there is no way of stopping

this. In order to ensure the lubrication of the air conditioner

compressor, the refrigerant oil quantity should be topped up

with fresh refrigerant oil

⇒ “2.6 Charging refrigerant circuit”, page 146 .

♦ Where vehicles are fitted with an air conditioner compressor

without a magnetic clutch (with air conditioner compressor

regulating valve - N280- ) the engine should be run with the

refrigerant circuit empty for no longer than is absolutely nec‐

essary, making sure that higher engine speeds are avoided

(since the air conditioner compressor will always run when the

engine is running).

♦ On vehicles that have an air c^lo^knditioner compressor without

magnetic clutch, the engine may only be started with a com‐

pletely assembled refrigerant circuit, ensuring that higher en‐

gine speeds are avoided.

♦ Depending on the version of air conditioner compressor, a

valve may be installed on the high-pressure side that prevents

liquefied refrigerant flowing back into the air conditioner com‐

pressor after the air conditioning system is switched off. If an

air conditioner compressor with this valve is installed in a ve‐

hicle with a refrigerant circuit with expansion valve, it could

take some time before the pressure on the high-pressure side

drops (the expansion valve is cold and the pressure on the

low-pressure side rises quickly after switching off, the expan‐

sion valve closes and refrigerant only flows slowly on the low-

pressure side). If the air conditioner compressor is switched

on (or the refrigerant circuit is emptied via the low pressure

side), pressure on the low pressure side drops, the expansion

valve opens and refrigerant can flow on the low pressure side.

If it is necessary after emptying to perform work on the vehicle for

which the air conditioner service station is not required:

– Detach the air conditioner service station from the refrigerant

circuit and switch off

⇒ “2.8 Switching off air conditioner service station and sepa‐

rating from refrigerant circuit”, page 151 .

– Open the refrigerant circuit at a connection point.

CAUTION

Risk of freezing injury caused by escaping pressurised refrig‐

erant.

There is a risk of injury to the skin and parts of the body due to

freezing.

– Wear protective gloves.

– Wear protective goggles.

– Extract refrigerant and open the refrigerant circuit immedi‐

ately afterwards.

– If more than 10 minutes have passed since the refrigerant

was extracted, repeat the extraction process before opening

the refrigerant circuit. Pressure could build up in the refrig‐

erant circuit from continued evaporation.

– Perform the required measures on the refrigerant circuit.

If, after emptying, the refrigerant circuit is to be evacuated and

recharged ⇒ “2.5 Evacuating refrigerant circuit”, page 140 .

2. Working with air conditioner service station

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Note

♦ After opening the connecting points in the refrigerant circuit,

the open lines and component connections must be closed (so

that the ingress of moisture and dirt in these components is

prevented).

♦ Sometimes, refrigerant oil is extracted from the refrigerant cir‐

cuit along with the refrigerant and there is no way of stopping

this. To ensure lubrication of the air conditioner compressor,

the refrigerant oil quantity should be topped up with fresh oil.

lk

♦ Where vehicles are fitted with an air conditioner compressor

with air conditioner compressor regulating valve - N280- , the

engine should be run with the refrigerant circuit empty for no

longer than is absolutely necessary, making sure that higher

engine speeds are avoided (since the air conditioner com‐

pressor will always run when the engine is running).

♦ On vehicles that have an air conditioner compressor with air

conditioner compressor regulating valve - N280- , the engine

may only be started with a completely assembled refrigerant

circuit, ensuring that higher engine speeds are avoided.

2.5

Evacuating refrigerant circuit

•

The procedure described in the operating manual for your air

conditioning service station is to be followed ⇒ Operating

manual for air conditioner service station .

The refrigerant oil volume in the air conditioner service station

has been checked and, if necessary, adjusted ⇒ Operating

instructions of air conditioner service station .

The refrigerant volume in the air conditioner service station

has been checked and, if necessary, adjusted ⇒ Operating

manual of air conditioner service station .

Before the refrigerant circuit is filled with refrigerant, it must be

evacuated, i.e. completely emptied of air. In the process, all mois‐

ture is drawn out of the circuit.

Leaks can be determined when evacuating the refrigerant circuit

⇒ “1.4 Investigating leaks”, page 68 .

NOTICE

Risk of damage to air conditioner compressor with negative

pressure in the refrigerant circuit.

– Never start the engine if there is negative pressure in the

refrigerant circuit.

Evacuating:

•

The refrigerant circuit is completely assembled.

– On vehicles with high-voltage system, switch off stationary air

conditioning function (deactivate) ⇒ Owner's Manual .

– Switch off ignition.

– Connect the air conditioner service station to the power sup‐

ply.

In addition for vehicles with electrically-actuated valves in the re‐

frigerant circuit that are not open when de-energised:

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Note

lk

♦ On vehicles with high-voltage system and auxiliary air condi‐

tioning system functions (“heat pump mode” or “cooling of

high-voltage battery”), valves may be installed in the refriger‐

ant circuit that are not open when de-energised. These valves

are opened and closed e.g. via incremental motors and are no

longer actuated when the ignition is switched off. To empty

completely, to evacuate correctly and to charge the refrigerant

circuit, however, no areas may be isolated, which is why these

valves must be opened before work is carried out ⇒ Heating,

air conditioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-spe‐

cific workshop manual) and ⇒ Vehicle diagnostic tester in

“Guided Fault Finding” mode.

♦ Non-return valves in the refrigerant circuit have a certain hold‐

ing pressure in the direction of flow (approx. 0.1 bar or

100 mbar). To ensure that the refrigerant circuit can be evac‐

uated completely (residual pressure below 5 mbar), all of the

electrically actuated valves must therefore be open.

– Use the vehicle diagnostic tester to open the electrically-ac‐

tuated valves that are not open when de-energised ⇒ Vehicle

diagnostic tester in “Guided Fault Finding” mode.

All vehicles

– Bring the air conditioner service station into operation as de‐

scribed in the instructions ⇒ Operating instructions air condi‐

tioner service station .

– Unscrew the sealing caps from the service connections of the

refrigerant circuit (see vehicle-specific refrigerant circuit) ⇒

Heating, air conditioning system; Rep. gr. 87 ; Refrigerant cir‐

cuit (vehicle-specific workshop manual).

– Check service connections of refrigerant circuit for contami‐

nation or corrosion, clean if necessary.

Note

Dirt or a rough surface on the service connections caused by cor‐

rosion can cause damage to the seals and thereby premature

failure of the quick-release couplings.

– Connect the air conditioner service station to the refrigerant

circuit

⇒ “2.2 Connecting air conditioner service station to refrigerant

circuit”, page 131 .

– Switch on the air conditioner service station , evacuate the re‐

frigerant circuit and perform the vacuum test (for a period of

e.g. 10 minutes with the vacuum pump on to remove any air,

remains of refrigerant and moisture and 20 minutes for the

vacuum/pressure increase check).

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Note

♦ The vacuum at the end of the evacuating process (running of

vacuum pump of air conditioner service station ) must be less

than 5 mbar absolute pressure. Should pressure during the

evacuating process in the refrigerant circuit not be less than

5 mbar, this could have various causes. For example, leaks in

the refrigerant circuit or in the connection to the air conditioner

service station , the time for the evacuating process is set too

short, the vacuum pump of the air conditioner_lkservice station

does not generate the necessary vacuum or the vacuum sen‐

sor of the air conditioner service station is not calibrated prop‐

erly ⇒ Operating instructions air conditioner service station .

♦ An absolute pressure of 5 mbar equates to a vacuum of

975 mbar at an ambient pressure e.g. of 980 mbar.

♦ At the end of the vacuum/pressure increase check, pressure

in the refrigerant circuit should not be greater than 20 mbar

absolute. Should the pressure in the refrigerant circuit be

greater than 20 mbar during the vacuum/pressure increase

check, the vacuum pump is switched on and the process is

repeated from the beginning ⇒ Operating instructions air con‐

ditioner service station . Should pressure in the refrigerant

circuit still not be less than 20 mbar even after the process has

been repeated twice, this could have various causes. For ex‐

ample, there could be leaks in the refrigerant circuit, a leak in

the connection from the refrigerant circuit to the air conditioner

service station or in the air conditioner service station itself,

the time set for the evacuating process is too short and the

time set for the vacuum/pressure increase check is too long.

♦ If there is reason to suspect a leak in the refrigerant circuit,

switch off the air conditioner service station if necessary and

allow it to stand for as long as possible (e.g. for at least 1 hour

to check the leak-tightness of the refrigerant circuit) ⇒ Oper‐

ating instructions air conditioner service station .

♦ Depending on the version of air conditioner service station ,

the pressure in the refrigerant circuit is displayed directly.

However, there is also a chance that the current pressure is

only displayed while the vacuum pump is running ⇒ Operating

instructions air conditioner service station . In the event of an

air conditioner service station only displaying the ambient

pressure, the display of the pressure in the refrigerant circuit

will depend on the ambient pressure during activation (ambi‐

ent pressure at 980 mbar, a vacuum of 975 mbar equates to

a residual pressure of 5 mbar absolute).

♦ If the refrigerant circuit was opened, small quantities of mois‐

ture may have entered the refrigerant circuit. In this case, the

refrigerant circuit is to be evacuated for at least 30 minutes

(pressure in the refrigerant circuit before charging must be less

than 20 mbar).

♦ If the refrigerant was extracted (to check the fill volume) and

the refrigerant circuit was only evacuated so that it could be

recharged (the refrigerant circuit was not opened and is leak-

tight), it is sufficient to evacuate the refrigerant circuit for 5

minutes and to set no time or only a short time (e.g. 1 minute)

for the vacuum/pressure increase check (no air or moisture

entered the refrigerant circuit).

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♦ Depending on the volume of refrigerant oil in the refrigerant

circuit, the age and mileage of the vehicle, the layout of the

refrigerant circuit etc., there is a chance with a leak-tight re‐

frigerant circuit of the specified absolute pressure in the re‐

frigerant circuit not rising above the prescribed 20 mbar owing

to refrigerant evaporating out of the refrigerant oil. Should this

be the case, repeat the process again if necessary and / or

adapt the preset times accordingly.

If the vacuum display does not change (and the pressure stays

below 20 mbar), the system is leak-tight and can be recharged.

lk

Note

♦ Depending on the version of air conditioner service station ,

the current pressure in the refrigerant circuit is permanently

displayed or only displayed after switching on e.g. the “Evac‐

uate” function ⇒ Operating instructions air conditioner service

station .

♦ Due to the high degree of evacuation, there is a chance that

refrigerant - which evaporates from the refrigerant oil - could

elevate the pressure in the refrigerant circuit during the vac‐

uum test from 20 to 40 mbar (absolute pressure). This is no

indication of a leak in the refrigerant circuit, though depending

on the version of air conditioner service station it could trigger

a fault. If necessary, evacuate the refrigerant circuit again and

observe the vacuum display for an extended period. Only if the

vacuum remains steady and you are certain that the refriger‐

ant circuit is leak-tight is it permissible to charge the system.

– Charge the refrigerant circuit with air conditioner service sta‐

tion ⇒ “2.6 Charging refrigerant circuit”, page 146 .

If the vacuum does not remain or sufficient pressure cannot be

built-up, the following action is required:

♦ If pressure in the refrigerant circuit only rises slowly after evac‐

uating e.g. owing to refrigerant (or moisture) evaporating from

the refrigerant oil, evacuate the refrigerant circuit again and

observe the vacuum gauge for an extended period.

– If there is any doubt as to whether the refrigerant circuit is ac‐

tually leak-tight, evacuate again and observe the vacuum

gauge for an extended period. Only when a vacuum is main‐

tained can charging commence.

– Only if you are really sure that the refrigerant circuit is leak-

tight should the system be charged

⇒ “2.6 Charging refrigerant circuit”, page 146 .

Further action if a leak is detected during evacuation:

♦ If there is a leak so major that it causes air to escape to such

a degree during evacuation that the air conditioner service

station is incapable of generating a sufficient vacuum or the

vacuum gauge indicates immediately after switching off the air

conditioner service station that air has entered the system and

negative pressure is lost.

– Investigate the leak in the refrigerant circuit as follows:

2. Working with air conditioner service station

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Note

♦ A larger leak in the refrigerant circuit can be detected, for ex‐

ample, by pressurising the circuit to a maximum of 15 bar using

cleaned and dried compressed air or nitrogen ⇒ page 124 . If

the leak is large enough, the leakage point can be detected by

sound as the gas escapes.

♦ The compressed air or nitrogen is introduced to the closed,

empty refrigerant circuit via the service connection -B- to which

through a quick-release coupling adapter -A- has been con‐

nected.

lk

♦ Screw the handwheel -C- into the quick-release coupling

adapter -A- until the valve in the service connection -B- is

completely open - do not over tighten the valve.

♦ The quick-release coupling adapter for service connection can

be fitted e.g. with a modified charging hose -A- (for example

with a M12 x 1.5-6G thread in accordance with SAE J639)

depending on the thread of the quick-release coupling adapter

and a suitable adapter -B- to connect to the workshop com‐

pressed air system ⇒ page 259 . To ensure that no moisture,

oil and dirt from the workshop compressed air system enter

the refrigerant circuit of the air conditioning system, use e.g. a

combination fine filter unit for compressed air systems with an

oil, dirt and water separator, which is commonly used in paint

spraying facilities. Install this between the compressed air sys‐

tem and the charge hose -A- ⇒ Electronic parts catalogue .

♦ Using the manifold gauge with pressure reducer for nitrogen

(maximum reduced pressure: 15 bar) -1- you can connect a

full nitrogen gas cylinder -3- via a charge hose -2- (e.g. with

M12 x 1.5-6G thread in accordance with SAE J639) to the

service connection - to which a quick-release coupling adapter

is connected - of a closed, empty refrigerant circuit

⇒ page 258 .

– Slowly increase the pressure in the refrigerant circuit to a max‐

imum of 15 bar.

CAUTION

Risk of injury from nitrogen escaping under high pressure.

– Use pressure limiter for nitrogen tank.

– Search for the leak by sound, which can be heard as gas es‐

capes from this point.

– Repair the leak.

– Evacuate refrigerant circuit and observe the vacuum gauge

over a period of hours. Only when a vacuum is maintained can

charging commence.

♦ If a leak is present of a size where no or very little air is drawn

in - with the refrigerant circuit evacuated - and the air condi‐

tioner service station can create sufficient vacuum. The vac‐

uum gauge does not increase or increases very slowly after

switching the air conditioner service station off. This indicates

that there may be a very small ingress of air and the vacuum

is lost.

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– Charge the circuit with 100 g of refrigerant and search for the

possible leak using an electronic leak tester

⇒ “1.4.2 Searching for leaks in refrigerant circuits using an

electronic leak detector”, page 69 or add an approved UV

contrast substance to the refrigerant and search for the pos‐

sible leak in the circuit using the leak detector system

⇒ “1.4.3 Searching for leaks with UV leak detection system”,

page 71 .

– Evacuate refrigerant circuit if necessary

⇒ “2.4 Emptying refrigerant circuit”, page 137

– Rectify the problem in the refrigerant circuit ⇒ Heating, air

conditioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-specific

workshop manual).

– Evacuate the refrigerant circuit and observe the vacuum

gauge over an extended period. Only when a vacuum is main‐

tained can charging commence

lk

⇒ “2.5 Evacuating refrigerant circuit”, page 140 .

If it is necessary after evacuating to perform work on the vehicle

for which the air conditioner service station is not required:

– Detach the air conditioner service station from the refrigerant

circuit and switch off

⇒ “2.8 Switching off air conditioner service station and sepa‐

rating from refrigerant circuit”, page 151 .

NOTICE

Risk of damage to air conditioner compressor with negative

pressure in the refrigerant circuit.

– Never start the engine if there is negative pressure in the

refrigerant circuit.

– Ensure that, until the refrigerant circuit is charged, the engine

cannot be started.

If after emptying and evacuating the refrigerant circuit is to be

recharged ⇒ “2.6 Charging refrigerant circuit”, page 146 .

2.6

Charging refrigerant circuit

Note

♦ The whole amount of refrigerant can be charged either on the

high pressure side or the low pressure side. Charging of the

refrigerant circuit is described as follows for the high pressure

side.

♦ Fill capacities of refrigerant and refrigerant oil ⇒ Heating, air

conditioning; Rep. gr. 00 ; Technical data .

•

The procedure described in the instruction manual for the air

conditioning service station is to be followed ⇒ Operating in‐

structions of air conditioner service station .

Before charging the system with refrigerant, the amount of re‐

frigerant oil must be adjusted ⇒ Heating, air conditioning; Rep.

gr. 00 ; Technical data .

Ensure when charging the refrigerant circuit that the air con‐

ditioner service station is at the same level as the vehicle

whose refrigerant circuit is to be charged (no greater than 50

cm difference). If the height difference is too great, deviations

may occur between the amount of refrigerant displayed and

the amount actually charged (depending on the version of air

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conditioner service station ). The filling accuracy of the air

conditioner service station may be affected.

•

The refrigerant circuit is completely assembled ⇒ Heating, air

conditioning; Rep. gr. 87 ; Refrigerant circuit; System over‐

view - refrigerant circuit .

– On vehicles with high-voltage system, switch off stationary air

conditioning function (deactivate) ⇒ Owner's Manual .

– Switch off ignition.

– Connect the air conditioner service station to the power sup‐

ply.

– Check the volume of refrigerant, the volume of refrigerant oil

and the amount of UV leak detection additive in the air condi‐

tioner service station and replenish as necessary ⇒ Operating

instructions air conditioner service station .

In addition for vehicles with electrically-actuated valves in the re‐

frigerant circuit that are not open when de-energised:

Note

On vehicles with high-voltage system and auxiliary air condition‐

ing system functions (“heat pump mode” or “cooling of high-

voltage battery”), valves may be installed in the refrigerant circuit

that are not open when de-energised. These valves are opened

and closed e.g. via incremental motors and are no longer actu‐

ated when the ignition is switched off. To empty the refrigerant

circuit completely or to evacuate and charge it correctly, however,

no areas must be isolated. Therefore, these valves must be

opened before performing these types of work ⇒ Heating, air

conditioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-specific

workshop manual) and ⇒ Vehicle diagnostic tester in “Guided

Fault Finding” mode.

– Use the vehicle diagnostic tester to open the electrically-ac‐

tuated valves that are not open when de-energised ⇒ Vehicle

diagnostic tester in “Guided Fault Finding” mode.

All vehicles

– Bring the air conditioner service station into operation as de‐

scribed in the instructions ⇒ Operating instructions air condi‐

tioner service station .

– Unscrew the sealing caps from the service connections of the

refrigerant circuit (see vehicle-specific refrigerant circuit) ⇒

Heating, air conditioning system; Rep. gr. 87 ; Refrigerant cir‐

cuit (vehicle-specific workshop manual).

– Connect quick-release couplings to the service connections of

the refrigerant circuit

⇒ “2.2 Connecting air conditioner service station to refrigerant

circuit”, page 131 .

– Evacuate the refrigerant circuit with the air conditioner service

station ⇒ “2.5 Evacuating refrigerant circuit”, page 140 .

– Adjust the requisite amount of refrigerant, the amount of re‐

frigerant oil to be replenished if necessary and the amount of

UV leak detection additive in the air conditioner service station

⇒ Operating instructions air conditioner service station , ⇒

Heating, air conditioning; Rep. gr. 00 ; Technical data (vehicle-

specific workshop manual).

– Choose the relevant setting on the air conditioner service sta‐

tion for charging on the high pressure side ⇒ Operating

instructions air conditioner service station .

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When charging the refrigerant circuit on the low pressure side,

liquefied refrigerant could accumulate in the compression cham‐

ber of the air conditioner compressor.

– Should it be necessary to charge the refrigerant circuit on the

low pressure side, turn the air conditioner compressor 10

times by hand before bringing into operation for the first time

after charging (if necessary, remove e.g. the drive belt to fa‐

cilitate this).

Note

♦ Refrigerant and refrigerant oil are charged in the refrigerant

circuit on the high pressure side.

♦ If a vehicle has no service connection on the high pressure

side of the refrigerant circuit, refrigerant can also be charged

via the service connection on the low pressure side. To do this,

lk

however, always observe the setting and the operating in‐

structions of the air conditioner service station .

♦ If on an air conditioner service station the charging device

cannot be adjusted, unscrew (close) the handwheel on the

quick-release coupling adapter on the low pressure side if

necessary.

– Charge the refrigerant circuit with the requisite amount of re‐

frigerant, the amount of refrigerant oil that needs to be replen‐

ished if necessary and the amount of UV leak detection

additive.

– Bring the air conditioning system into operation after charging

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit;

Bringing air conditioning system into operation after charging

refrigerant circuit (vehicle-specific workshop manual) and

⇒ “2.7 Bringing air conditioning system into service after

charging”, page 149

Bringing air conditioning system with electrical air conditioning

compressor into operation

– Bring the air conditioner compressor into operation via “Basic

setting, compressor run-in” function in guided fault finding

⇒ Vehicle diagnostic tester.

In addition for vehicles with electrically-actuated valves in the re‐

frigerant circuit that are not open when de-energised:

– Use the vehicle diagnostic tester to enable (open or close) the

electrically-actuated valves - that are not open when de-ener‐

gised - for operation of the air conditioning system via the

respective control unit ⇒ Vehicle diagnostic tester in “Guided

Fault Finding” mode.

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Note

On vehicles with high-voltage system and auxiliary air condition‐

ing system functions (“heat pump mode” or “cooling of high-

voltage battery”), valves may be installed in the refrigerant circuit

that are not open when de-energised. These valves are opened

and closed e.g. via incremental motors and are no longer actu‐

ated when the ignition is switched off. To completely empty,

correctly evacuate and charge the refrigerant circuit, however, no

areas may be isolated. Therefore, these valves must be opened

before these measures are carried out. On completion of the

work, enable actuation of these valves again via the respective

control unit ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant

circuit (vehicle-specific workshop manual) and ⇒ Vehicle diag‐

nostic tester in “Guided Fault Finding” mode.

All vehicles

If it is necessary to perform a function check after charging the

refrigerant circuit:

lk

– Check the pressures in the refrigerant circuit ⇒ page 170 .

If it is not necessary to perform a function check after charging

the refrigerant circuit:

– Detach the air conditioner service station from the refrigerant

circuit and switch off

⇒ “2.8 Switching off air conditioner service station and sepa‐

rating from refrigerant circuit”, page 151 .

2.7

Bringing air conditioning system into

service after charging

Note

♦ If the mechanical air conditioner compressor was removed,

turn it approx. 10 times by hand before initial operation (during

installation or after installation e.g. before fitting the belt) so

that no damage is caused from a fluid shock when it is switch‐

ed on the first time (if there is refrigerant oil in the cylinder of

the air conditioner compressor, this will be forced out by turn‐

ing) ⇒ Heating, air conditioning; Rep. gr. 87 ; Air conditioner

compressor; Removing and installing air conditioner compres‐

sor .

♦ If the electrical air conditioner compressor was removed, be‐

fore bringing the air conditioning system into operation for the

first time and after charging, the air conditioner compressor is

to be brought into operation via the “Basic setting, compressor

run-in” function in guided fault finding ⇒ Vehicle diagnostic

tester in “Guided Fault Finding” mode - air conditioning system

and battery regulation. This prevents damage to the air con‐

ditioner compressor, e.g. from a fluid shock, during initial

activation (if there is refrigerant oil in the compression cham‐

ber of the air conditioner compressor, this will be forced out).

♦ The mechanical air conditioner compressor is driven by the

engine via a belt or a shaft. The electrical air conditioner com‐

pressor is driven by an electric motor mounted directly on the

air conditioner compressor (e.g. on vehicles with hybrid drive)

⇒ Heating, air conditioning; Rep. gr. 87 ; Air conditioner com‐

pressor; Removing and installing air conditioner compressor .

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Bringing air conditioning system with mechanical air conditioning

compressor into operation

– Switch on ignition.

– Set the air conditioning system to the lowest output possible

(e.g. select operating mode “A/C OFF”).

– Switch off actuation of the air conditioner compressor (e.g.

select operating mode “A/C OFF”).

– Start the engine with the air conditioner compressor switched

off (e.g. operating mode “A/C OFF” selected).

– Wait until idling speed has stabilised:

– Switch air conditioner compressor on and let system run for at

least 2 minutes with engine idling.

– If necessary, check the pressures in the refrigerant circuit us‐

ing the air conditioner service station ⇒ page 129 .

– Switch off engine.

– Detach the air conditioner service station from the refrigerant

circuit and switch off

⇒ “2.8 Switching off air conditioner service station and sepa‐

rating from refrigerant circuit”, page 151 .

Bringing air conditioning system with electrical air conditioning

compressor into operation

– Switch on ignition.

– Bring the air conditioner compressor into operation via the

“Basic settings, compressor run-in” function of guided fault

finding ⇒ Vehicle diagnostic tester in “Guided Fault Finding”

mode - air conditioning system and battery regulation.

In addition for vehicles with electrically-actuated valves in the re‐

frigerant circuit that are not open when de-energised:

– Use the vehicle diagnostic tester to enable (open or close) the

electrically-actuated valves - that are not open when de-ener‐

gised - for operation of the air conditioning system via the

respective control unit ⇒ Vehicle diagnostic tester in “Guided

Fault Finding” mode.

Note

On vehicles with high-voltage system and auxiliary air condition‐

ing system functions (“heat pump mode” or “cooling of high-

voltage battery”), valves may be installed in the refrigerant circuit

that are not open when de-energised. These valves are opened

and closed e.g. via incremental motors and are no longer actu‐

ated when the ignition is switched off. To completely empty,

correctly evacuate and charge the refrigerant circuit, however, no

areas may be isolated. Therefore, these valves must be opened

before these measures are carried out. On completion of the

work, enable actuation of these valves again via the respective

control unit ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant

circuit; System overview - refrigerant circuit and ⇒ Vehicle diag‐

nostic tester in “Guided Fault Finding” mode.

All air conditioning systems with electrical air conditioning com‐

pressor

– After the basic setting, check the pressures in the refrigerant

circuit if necessary using the air conditioner service station .

– On vehicles with high-voltage system, switch off “stationary air

conditioning” function (deactivate)⇒ Owner's Manual .

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– Switch off ignition.

– Detach the air conditioner service station from the refrigerant

circuit and switch off

⇒ “2.8 Switching off air conditioner service station and sepa‐

rating from refrigerant circuit”, page 151 .

lk

Vehicles with electrical air conditioning compressor

•

The engine may only be started when the refrigerant circuit

has been fully assembled.

•

On vehicles with battery cooling, hybrid operation is only pos‐

sible with the air conditioning system charged and no faults

stored in connection with the air conditioning system ⇒ Vehicle

diagnostic tester in “Guided Fault Finding” mode - air condi‐

tioning system and battery regulation.

•

First bring the electrical air conditioner compressor into oper‐

ation after installing the air conditioner compressor and charg‐

ing the refrigerant circuit via the “Compressor run-in” function

in basic settings. Should there be an accumulation of refriger‐

ant oil in the compression chamber of the air conditioner

compressor before installation owing to unfavourable storage,

damage could be caused to the air conditioner compressor

⇒ Vehicle diagnostic tester in “Guided Fault Finding” mode -

air conditioning system and battery regulation.

An electrically driven air conditioner compressor may only be

activated when the refrigerant circuit is charged. Running the

air conditioner compressor with the refrigerant circuit empty

could lead to compressor damage ⇒ Vehicle diagnostic tester

in “Guided Fault Finding” mode - air conditioning system and

battery regulation.

– To minimise the number of automatic engine starts when the

vehicle's drive system is active (READY) during test and

measurement work, charge the vehicle batteries e.g. with the

battery charger 60 A - VAS 5904- in battery standby mode ⇒

Electrical system - General information; Rep. gr. 27 ; Charging

battery and ⇒ Electrical system; Rep. gr. 93 ; General warn‐

ings for work on the high-voltage system .

– For test and measurement work that requires the vehicle's

drive system to be active (READY) or the ignition to be switch‐

ed on, move the selector lever to position “P”, activate the

parking brake and arrange the tools needed so that they can‐

not come into contact with moving components of the engine

and so that they cannot even come near to components that

turn when the engine is running.

2.8

Switching off air conditioner service sta‐

tion and separating from refrigerant cir‐

cuit

– Finish the requisite work with the air conditioner service sta‐

tion .

– Switch off ignition.

– Unscrew (close) the handwheels of both service couplings.

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CAUTION

Risk of freezing injury caused by escaping pressurised refrig‐

erant.

There is a risk of injury to the skin and parts of the body due to

freezing.

– Wear protective gloves.

– Wear protective goggles.

– If, when loosening the handwheel of the service coupling,

refrigerant escapes from the refrigerant line for longer than

1 second, screw in the handwheel and renew the defective

valve.

– Extract refrigerant and open the refrigerant circuit immedi‐

ately afterwards.

– If more than 10 minutes have passed since the refrigerant

was extracted, repeat the extraction process before opening

the refrigerant circuit. Pressure could build up in the refrig‐

erant circuit from continued evaporation.

lk

Different versions of service couplings

♦ On one version of service coupling, the space between the

valve in the service connection of the refrigerant circuit and the

valve in the service coupling is vented externally when the

handwheel is unscrewed. On these service couplings, the

valve in the service connection of the vehicle is closed first,

followed by the valve in the service coupling for the charge

hose of air conditioner service station when the handwheel of

the service coupling is unscrewed. As it is unscrewed further,

the pressure still present between the two valves is released

3

via an additional valve (approx. 2 cm of refrigerant). Should

one of these two valves (the valve in the service connection of

the vehicle or the valve in the service coupling for the charge

hose) not close properly, the whole refrigerant could escape

out of the refrigerant circuit of the vehicle or the charge hose.

♦ On another version of service coupling, the space between the

valve in the service connection of the refrigerant circuit and the

valve in the service coupling is not vented externally when the

handwheel is unscrewed. This version features a valve that is

open when the service coupling is connected, which facilitates

pressure compensation between the space to the valve in the

service connection of the refrigerant circuit and the charge

hose connected to the service coupling. On this version, no

refrigerant escapes when the handwheel of the service cou‐

pling is unscrewed, which is why the refrigerant has to be

extracted from the charge hoses into the air conditioner serv‐

ice station here before the service couplings are disconnected.

If a large amount of refrigerant is recovered here, for example,

after a pressure test or after charging the refrigerant circuit

(more than approx. 50 g), this is an indication that a valve in

one of the service connections of the refrigerant circuit could

be leaking and refrigerant is escaping from the refrigerant cir‐

cuit of the vehicle (extract refrigerant and renew the defective

valve)

Before extracting the refrigerant from the charge hoses into the

air conditioner service station , unscrew the handwheels of both

service couplings as far as they will go.

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Note

♦ Stored in the air conditioner service station is a function via

which it is switched to a specific operating mode when deac‐

tivated. The whole refrigerant is extracted from the charge

hoses into the air conditioner service station with this function.

♦ If the handwheels of the two service couplings are not un‐

lk

screwed when this function is activated, refrigerant could be

extracted from the vehicle's refrigerant circuit.

– Extract the refrigerant from the two charge hoses using the air

conditioner service station as instructed in the relevant oper‐

ating manual ⇒ Operating instructions of air conditioner serv‐

ice station .

Note

♦ If, on an air conditioner service station with a service coupling

that does not vent to the outside, this process takes longer

than approx. 2 minutes or quite a large amount of refrigerant

is extracted, this suggests that there is a fault in one of the

valves in a service connection.

♦ If, on an air conditioner service station with a service coupling

that does vent to the outside, this process takes longer than

approx. 2 minutes, this suggests that there is a fault in one of

the valves in a service coupling.

Note

Erroneous extraction from vehicle's refrigerant circuit.

– First unscrew (close) the handwheels of the quick-release

coupling adapters.

– Then extract the refrigerant from the two charge hoses using

the air conditioner service station.

– Switch off the air conditioner service station (and isolate it from

the power supply if necessary) ⇒ Operating instructions air

conditioner service station .

– Separate the quick-release couplings from the service con‐

nections of the refrigerant circuit.

– Screw the sealing caps on the service connections (see vehi‐

cle-specific refrigerant circuit) ⇒ Heating, air conditioning;

Rep. gr. 87 ; Refrigerant circuit; System overview - refrigerant

circuit .

2.9

Charging refrigerant in reservoir

– Connect the cylinder with fresh R1234yf refrigerant to the

service coupling on the high pressure side of the air condi‐

tioner service station ⇒ Operating instructions air conditioner

service station .

– Perform a gas analysis on the refrigerant (from the cylinder

supplied) with which the system is to be charged using the air

conditioner service station

⇒ “2.3 Performing gas analysis of refrigerant”, page 134 .

•

The procedure described in the operating manual for your air

conditioning service station is to be followed ⇒ Operating

manual for air conditioner service station .

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CAUTION

Risk of explosion from overfilling refrigerant reservoirs.

Refrigerant can expand and cause reservoirs to burst if they are

overfilled.

– Use a refrigerant tank with safety valve.

– Never exceed the permissible fill level of the refrigerant tank.

Note

Depending on the version of air conditioner service station and

the measures to be performed, there is a minimum volume of re‐

frigerant, refrigerant oil and UV leak detection additive that must

be in the respective supply tank of the air conditioner service sta‐

tion ⇒ Operating instructions air conditioner service station

2.10

Emptying air conditioner service station

Note

♦ If it is necessary to discharge the air conditioner service station

lk

(e.g. because contaminated refrigerant was extracted), all fil‐

ters and dryers must be renewed (do not remove filter and

dryer from the air-tight transport package until immediately

before installation to keep absorption of moisture as low as

possible).

♦ If it is necessary to empty the air conditioner service station

(e.g. because certain measures have to be performed on the

air conditioner service station and the refrigerant that has been

or is to be extracted from the air conditioner service station

complies with the specifications (is not contaminated), it can

be filled into a recycling cylinder, if necessary, and then reused

⇒ Operating instructions air conditioner service station .

♦ Refrigerant cylinders that have been charged with contamina‐

ted or used refrigerant are referred to as “recycling cylinders”

or “R cylinders”.

♦ Always evacuate recycling cylinders before the first filling (re‐

frigerant cylinders containing air must not be filled with refrig‐

erant).

♦ Different types of refrigerant must not be mixed together (mix‐

tures of refrigerant cannot be recycled, but must be disposed

of instead). If the composition of the contents in the cylinder is

not clear, the gas processing / gas disposal company must be

informed of this

⇒ “2.13 Filling contaminated refrigerant in a recycling cylinder

for analysis, processing or disposal”, page 161 and

⇒ “6.2.17 Returning contaminated R1234yf refrigerant for

analysis, processing or disposal”, page 25 .

CAUTION

Risk of explosion from overfilling refrigerant reservoirs.

Refrigerant can expand and cause reservoirs to burst if they are

overfilled.

– Use a refrigerant tank with safety valve.

– Never exceed the permissible fill level of the refrigerant tank.

There are various ways to empty an air conditioner service sta‐

tion , observe the operating instructions of the air conditioner

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service station ⇒ Operating instructions air conditioner service

station .

– Drain the refrigerant from the air conditioner service station to

be emptied into a different air conditioner service station , ob‐

serving the operating instructions of the air conditioner service

station to do so ⇒ Operating instructions air conditioner serv‐

ice station and

⇒ “2.13 Filling contaminated refrigerant in a recycling cylinder

for analysis, processing or disposal”, page 161 .

2.11

Cleaning electrical air conditioning com‐

pressor

Vehicles with high-voltage system

Observe the additional warnings for working on vehicles with

high-voltage system ⇒ Electrical system; Rep. gr. 93 ; General

warnings for work on the high-voltage system .

If repair work in the vicinity of high-voltage components and ca‐

bles is necessary, carry out a visual check for damage on high-

voltage components and cables, and observe the warnings ⇒

Electrical system; Rep. gr. 93 ; General warnings for work on the

lk

high-voltage system .

If repair work on high-voltage components is necessary, de-en‐

ergise the high-voltage system ⇒ Electrical system; Rep. gr. 93 ;

De-energising high-voltage system , and “observe the general

warnings for work on the high-voltage system” ⇒ Electrical sys‐

tem; Rep. gr. 93 ; General warnings for work on the high-voltage

system .

Flushing air conditioner compressor

Note

♦ On an electrical air conditioning compressor, the refrigerant oil

cannot be poured out (as there is no oil drain plug), i.e. the

design makes no allowance for the drainage of oil

♦ With an electrical air conditioning compressor, the refrigerant

oil is to be removed in the direction of flow by flushing (flushing

in the opposite direction of flow is not possible due to the in‐

tegrated valves).

♦ The air conditioner compressor must be positioned for flushing

so that the connection for the refrigerant line on the high pres‐

sure side is at the lowest point possible.

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1 - Air conditioner service sta‐

tion

❑ With electronics and

flushing program, air

conditioner service sta‐

tion with flushing device

⇒ Electronic parts cata‐

logue .

❑ If an air conditioner

service station without

flushing program is

used, the sequence has

to be carried out man‐

ually (evacuate, flush

4 times with at least 2 kg

of refrigerant each time

and extract refrigerant

again, evacuate).

lk

2 - Refrigerant hose of air con‐

ditioner service station

❑ From high pressure side

of air conditioner service

station (normally col‐

oured red) for connect‐

ing low pressure side of

air conditioner compres‐

sor to refrigerant circuit

(larger diameter)

3 - Adapter to connection for

low pressure side on air condi‐

tioner compressor

❑ Different versions de‐

pending on vehicle

⇒ “1.6.8 Adapters for

setting up flushing cir‐

cuits”, page 105

❑ The item to be used be‐

tween the refrigerant

hose -2- and adapter -3- is adapter - VAS 6338/48- .

❑ From adapter case VW/Audi passenger vehicle set

4 - Refrigerant line

❑ For connection of air conditioner compressor to adapter ⇒ Item 3 (page 156)

5 - Electrical air conditioner compressor

❑ Flush the air conditioner compressor in normal direction of flow (from low pressure inlet to high pressure

outlet)

❑ In order to flush as much refrigerant oil out of the air conditioner compressor as possible, make sure that

the high pressure outlet of the air conditioner compressor is in the lowest position possible

Note

♦ Depending on the air conditioner

compressor, a new air condition‐

er compressor might be filled

with quite a large amount of re‐

frigerant oil (see manufacturer

plate on air conditioner compres‐

sor and

⇒ “5.2 Refrigerant oil capacities”,

page 15 ).

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♦ On a new air conditioner com‐

pressor filled with more than

150 cm³, pour out as much re‐

frigerant oil as possible before

flushing.

♦ Reason: The oil volume to be

displaced in one work step may

be restricted depending on the

version of air conditioner service

station .

Note

If the clean refrigerant oil is poured

out of a new air conditioner com‐

lk

pressor into a clean container and

this is subsequently sealed air-tight,

the refrigerant oil can be re-used to

top-up the refrigerant oil volume in

the circuit.

6 - Refrigerant line

❑ For connection of air conditioner compressor to adapter ⇒ Item 7 (page 157)

❑ Use a refrigerant line e.g. with part number 7L6 820 721 BF to set-up the flushing circuit ⇒ Electronic

parts catalogue

7 - Adapter for connection on high pressure side of air conditioner compressor

❑ Different versions depending on vehicle ⇒ “1.6.8 Adapters for setting up flushing circuits”, page 105

❑ From adapter case VW/Audi passenger vehicle set

8 - Charging hose of flushing device for refrigerant circuits

❑ From connection to high pressure side of air conditioner compressor on refrigerant circuit (smaller di‐

ameter) to inlet of flushing device for refrigerant circuits.

9 - Flushing device for refrigerant circuits

❑ Different versions and different design of flushing devices for refrigerant circuits ⇒ Electronic parts cata‐

logue (Tools; Workshop equipment/tools; Air conditioning/heating)

❑ With filter, sight glass, safety valve, heating, refrigerant tank, etc. (depending on version).

❑ Depending on the layout of the air conditioner service station and the flushing device for refrigerant

circuits, there may be a service coupling for refrigerant circuits fitted at the outlet and in some cases at

the inlet of the flushing device. If a service connection with a valve is installed to the outlet of the flushing

device, this valve must be opened completely when the service coupling is connected. If the valve is not

opened completely, it restricts the refrigerant flow.

❑ If there is a connection for a service coupling fitted at the inlet of the flushing device, the inlet must be

adapted to allow for the refrigerant hose coming from the vehicle to be connected directly.

Note

A service coupling and a valve in the

inlet of the flushing device restrict

the refrigerant flow from the vehicle

into the flushing device.

10 - Refrigerant hose of air conditioner service station

❑ From the low pressure side of the air conditioner service station (normally coloured blue) to the outlet of

the flushing device for refrigerant circuits.

2.12

Cleaning refrigerant circuit

– Perform preparatory measures for cleaning (flushing with

R1234yf refrigerant)

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⇒ “1.6.2 Preparations for cleaning refrigerant circuit (flushing

with R1234yf refrigerant)”, page 94

– Check the refrigerant volume in the air conditioner service sta‐

tion . There must be at least 6 kg of R1234yf refrigerant ⇒

Operating instructions of air conditioner service station .

– Empty container for used oil of air conditioner service station

⇒ Operating instructions of air conditioner service station .

– Connect the supply hose (high pressure side) of the air con‐

ditioner service station with an adapter to the low pressure line

leading to the air conditioner compressor (line with larger di‐

ameter)

⇒ “1.6.8 Adapters for setting up flushing circuits”, page 105 .

– Connect the return hose (low pressure or suction side) of the

air conditioner service station to the outlet of the flushing de‐

vice for refrigerant circuits.

– Connect the inlet of the flushing device for refrigerant circuits

with an adapter to the high pressure line leading to the air

lk

conditioner compressor (line with smaller diameter)

⇒ “1.6.8 Adapters for setting up flushing circuits”, page 105 .

♦ Principle circuit diagrams for various flushing circuits

⇒ “1.6 Cleaning refrigerant circuit”, page 92

♦ Adapters for setting up flushing circuits

⇒ “1.6.8 Adapters for setting up flushing circuits”, page 105

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Note

♦ The components are almost always flushed against the direc‐

tion of refrigerant flow when the air conditioning system is in

operation. (Exception: electrically-actuated air conditioner

compressor) ⇒ page 92 .

♦ When flushing, contaminants from the refrigerant circuit enter

the flushing device for refrigerant circuits and the air condi‐

tioner service station and are retained in the filters and dryers

installed within. Depending on the contamination, these com‐

ponents must be renewed at shorter intervals than prescribed

as per the operating instructions of the air conditioner service

station or flushing device for refrigerant circuits ⇒ Operating

lk

instructions of air conditioner service station .

♦ The filter in the flushing device for refrigerant circuits should

be changed (depending on the type and severity of contami‐

nation in the flushed refrigerant circuits) after about 5 to 10

flushing cycles (flushed vehicles). If a heavily contaminated

refrigerant circuit is flushed (the refrigerant oil from the refrig‐

erant circuit is black and viscous or there are large amounts

of swarf in the refrigerant circuit), renew the filter after flushing

this refrigerant circuit. After such heavy contamination of the

refrigerant circuit, it is a good idea to flush the system again

after replacing the filter.

♦ Depending on the type of contamination, deposits (old refrig‐

erant oil and friction dust from the air conditioner compressor)

will gather in the sight glass of the rinsing device for refrigerant

circuits. If necessary, clean this sight glass after flushing and

flush the refrigerant circuit through again to make sure it is

clean (one pass is sufficient in this instance).

♦ Liquid refrigerant cannot be routed through the expansion

valve, restrictor and desiccant bag of certain receivers at the

necessary rate. Therefore remove these components and re‐

place them with adapters if applicable ⇒ page 92 and ⇒

Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit;

System overview - refrigerant circuit (vehicle-specific work‐

shop manual).

♦ Adapters to connect air conditioner service station and to

bridge certain components of the refrigerant circuit

⇒ “1.6.8 Adapters for setting up flushing circuits”, page 105 .

Perform flushing (the procedure runs automatically as per the

program in the air conditioner service station ⇒ Operating in‐

structions of air conditioner service station )

– Switch on the air conditioner service station ⇒ Operating in‐

structions of air conditioner service station .

– Select the flushing program on the air conditioner service sta‐

tion ⇒ Operating instructions of air conditioner service station .

– Flush the refrigerant circuit (duration approx. 1 to 1.5 hours for

one flushing cycle with 4 cycles) ⇒ Operating instructions of

air conditioner service station .

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Note

♦ Flushing procedure

⇒ “1.6.3 Refrigerant circuit cleaning procedure”, page 96 .

♦ Perform flushing as instructed in the operating manual of the

air conditioning service station ⇒ Operating instructions of air

conditioner service station .

♦ Depending on the type of air conditioning service station , the

used oil tank has a capacity of about 125 cm ³of refrigerant

oil. If a system with a greater amount of refrigerant oil has to

be flushed, it may be necessary to empty the used oil tank after

the first flushing process of a flushing cycle.

♦ Observe the refrigerant flowing back into the air conditioning

service station from the refrigerant circuit. Once the refrigerant

flows clear and completely colourless through the inspection

window of the flushing device for refrigerant circuits in the air

conditioning service station , the refrigerant circuit is cleaned.

♦ When flushing, the whole amount of refrigerant oil from the

refrigerant circuit is washed out (except for a very small

amount, e.g. in the evaporator, but this is negligible).

♦ Where contamination is particularly high, it may be necessary

to carry out the flushing process twice (two flushing cycles with

4 flushing processes each).

– At the end of the flushing process, check the inspection win‐

dow or windows of the flushing device for refrigerant circuits.

If dirty, clean as per the instructions of the flushing device for

refrigerant circuits or air conditioner service station and per‐

form the flushing process again ^lt^ko be safe (running through

once over a period of approx. 30 min. is sufficient) ⇒ Operating

instructions air conditioner service station .

– Check the pressure in the refrigerant circuit. There must be no

overpressure in the refrigerant circuit (evacuate twice briefly if

necessary).

– Remove the connections to the air conditioning service station

from the refrigerant circuit of the vehicle (there should be no

overpressure in the refrigerant circuit)

– Renew these vehicle-specific components (restrictor and res‐

ervoir, expansion valve and receiver / dryer cartridge in the

reservoir) ⇒ Heating, air conditioning; Rep. gr. 87 ; Refriger‐

ant circuit; System overview - refrigerant circuit (vehicle-spe‐

cific workshop manual) and ⇒ Electronic parts catalogue .

– Depending on the complaint, renew the air conditioner com‐

pressor ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant

circuit; System overview - refrigerant circuit (vehicle-specific

workshop manual) and ⇒ Electronic parts catalogue or drain

the remaining refrigerant oil from the removed air conditioner

compressor ⇒ “1.5 Renewing components”, page 79 and fill

with the requisite amount of fresh refrigerant oil again ⇒ Heat‐

ing, air conditioning; Rep. gr. 00 ; Technical data (vehicle-

specific workshop manual) and ⇒ Heating, air conditioning;

Rep. gr. 00 ; Technical data; Refrigerant oil .

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Note

♦ Replacement compressors c_lo_kntain a certain specified quantity

of refrigerant oil. On vehicles with two evaporators, a certain

amount of refrigerant oil may also have to be filled in the circuit

if necessary ⇒ Heating, air conditioning; Rep. gr. 00 ; Tech‐

nical data; Refrigerant oil .

♦ If the air conditioner compressor does not need to be renewed,

replenish the refrigerant oil accordingly up to the prescribed fill

level (empty or flush refrigerant oil and pour the prescribed

volume back into the air conditioner compressor or refrigerant

circuit) ⇒ “1.5 Renewing components”, page 79 and ⇒ Heat‐

ing, air conditioning; Rep. gr. 00 ; Technical data; refrigerant

oil .

– Completely reassemble the refrigerant circuit again ⇒ Heat‐

ing, air conditioning; Rep. gr. 87 ; Refrigerant circuit; System

overview - refrigerant circuit (vehicle-specific workshop man‐

ual).

– Evacuate and charge the refrigerant circuit in accordance with

the specifications

⇒ “2.5 Evacuating refrigerant circuit”, page 140 ,

⇒ “2.6 Charging refrigerant circuit”, page 146 and ⇒ Heating,

air conditioning; Rep. gr. 00 ; Technical data .

– Bring the air conditioning system into operation in the prescri‐

bed manner ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrig‐

erant circuit; Bringing air conditioning system into operation

after charging refrigerant circuit (vehicle-specific workshop

manual) and

⇒ “2.7 Bringing air conditioning system into service after

charging”, page 149

2.13

Filling contaminated refrigerant in a re‐

cycling cylinder for analysis, processing

or disposal

⇒ “2.13.1 Filling contaminated refrigerant in a recycling cylinder

using technical equipment”, page 161

⇒ “2.13.2 Filling undercooled contaminated refrigerant in a recy‐

cling cylinder”, page 164

2.13.1

Filling contaminated refrigerant in a re‐

cycling cylinder using technical equip‐

ment

Note

♦ Some manufacturers may provide accessory devices (extract‐

ing or disposal units) that they claim to be approved for the

extraction of gases of unknown composition. These devices,

however, have not been tested or approved by Volkswagen

so that we cannot draw any conclusions about their operation

or suitability.

♦ In order to be filled into an evacuated recycling cylinder without

any auxiliary equipment, the contaminated refrigerant must be

supercooled. The corresponding procedure has been ap‐

proved by Volkswagen and described accordingly

⇒ page 164 .

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CAUTION

Risk of explosion if non-approved equipment is used

Refrigerant of unknown composition may expand due to a

chemical reaction or overheating causing the used device to

burst.

lk

– Make sure to use only devices and accessories that have

been authorised and approved by the manufacturer for be‐

ing suitable for operation with gases of unknown composi‐

tion in accordance with the relevant rules and regulations.

– Always read the owner's manual of these devices before

using them.

– Make sure to comply with all instructions given in the re‐

spective owner's manual when using the devices.

CAUTION

Risk of explosion from overfilling refrigerant reservoirs.

Refrigerant can expand and cause reservoirs to burst if they are

overfilled.

– Use a refrigerant tank with safety valve.

– Never exceed the permissible fill level of the refrigerant tank.

CAUTION

Chemical reactions from contaminated refrigerant. Mixing

gases of unknown composition can cause different chemical

reactions.

Risk of injuries.

– Never mix together refrigerants of different origins.

Extract refrigerant of unknown composition from refrigerant circuit

and collect it in a recycling cylinder.

– Connect the extracting and charging unit to the refrigerant cir‐

cuit of the vehicle and to a recycling cylinder observing the

corresponding owner's manual.

– Operate the extracting and charging unit according the in‐

structions in the corresponding owner's manual.

– Monitor the extraction process using a suitable pressure

gauge.

Note

♦ You can use your own pressure gauge or the pressure gauge

of the air conditioner service station to monitor the extraction

process.

♦ As it will take some time until the entire contaminated refrig‐

erant has been extracted from the refrigerant circuit, make

sure that you do not switch off the extracting and charging unit

until the refrigerant circuit has been drained completely. To be

absolutely sure about this, watch the display of the connected

pressure gauge.

After the entire contaminated refrigerant has been extracted from

the circuit:

– Switch off unit.

– Close the manual shut-off valve of the recycling cylinder.

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– Wait a certain amount of time (e.g. 20 minutes), then check if

pressure started building up again in the vehicle’s refrigerant

circuit.

Note

lk

If pressure started building up in the refrigerant circuit due to

evaporation of refrigerant, fill the refrigerant responsible for this

increase in pressure into the recycling cylinder.

– Remove the charge hose and adapter from the recycling cyl‐

inder, and seal the connection of the recycling cylinder with

the sealing cap.

– The paperwork required for analysis, processing (or disposal)

of contaminated refrigerant must be filled in completely (dis‐

posal record, acceptance certificate etc.).

Note

♦ All of the information and documents for analysis, processing

(or disposal) can be obtained from your gas processing / gas

disposal company.

♦ Included with the recycling cylinder is a form. Kindly fill this in

accordingly and attach it to the recycling cylinder.

♦ If it is not possible to weigh the recycling cylinder before and

after filling with contaminated refrigerant, the fill volume speci‐

fied for the vehicle in question can be quoted as the amount

of refrigerant that was filled in the recycling cylinder. This is

permissible as only the amount of refrigerant from a vehicle is

filled in a recycling cylinder.

– Take the recycling cylinder to a suitable location for storage

until it is ready to be collected by the gas processing / gas

disposal company.

– Fill out the data sheet for the recycling cylinder (R-cylinder) if

the refrigerant is contaminated, and firmly attach it to the re‐

cycling cylinder.

Note

♦ In the “Other comments” section, details can be provided re‐

garding e.g. who is to receive the analysis results and in which

way.

♦ Example for recycling cylinder (R-cylinder) data sheet

⇒ page 169 .

– Evacuate the refrigerant circuit with the air conditioner service

station for at least 1 hour

⇒ “2.5 Evacuating refrigerant circuit”, page 140 .

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Note

♦ Subsequent evacuation results in the last remnants of conta‐

minated refrigerant, which could still be in the refrigerant oil,

being removed at an absolute pressure of less than 10 mbar.

♦ If, after the unit has been switched off, a pressure that is higher

than the maximum permissible pressure for the function

“Evacuate” to be started on the air conditioner service station

builds up in the refrigerant circuit, release this pressure (drain

refrigerant) into the workshop extraction unit.

♦ The next steps depend on the complaint with the refrigerant

circuit

⇒ “2.3 Performing gas analysis of refrigerant”, page 134 .

2.13.2

Filling undercooled contaminated refrig‐

erant in a recycling cylinder

Note

♦ To ensure that the contaminated refrigerant is filled automat‐

ically without supporting equipment into an evacuated recy‐

cling cylinder, the cylinder must be supercooled.

♦ To cool down the evacuated recycling bottle, use an insulated

container and dry ice.

♦ Dry ice is solid carbon dioxide (CO ) that changes from a solid

2

lk

directly to a gaseous state at -78°C.

♦ Most of the gases used as refrigerant have only a low vapour

pressure at very low temperatures (less than 0.6 bar absolute

pressure at -50°C). When an extremely cooled recycling cyl‐

inder is connected to a refrigerant circuit, the refrigerant liq‐

uefies in the cold recycling cylinder and the pressure in the

refrigerant circuit drops below ambient pressure

⇒ “6.1.3 Vapour pressure table for refrigerant”, page 17 .

♦ Commercially available recycling cylinders are usually made

of common mild steel. These are not always suitable for low

temperatures (down to -78°C in this case), which is why only

recycling cylinders suitable for this application should be used

and why the cylinder should be allowed to reach ambient tem‐

perature slowly (e.g. by placing the insulated container with

recycling cylinder in a secure, well-ventilated location where

the dry ice can evaporate safely).

Special tools and workshop equipment required

♦ Extraction unit - VAS 581 007- ⇒ Electronic parts

catalogue (ETKA)

♦ At least 10 kg of commercially available dry ice (pellets or

granules)

♦ Evacuated recycling cylinder from gas supplier for contami‐

nated R1234yf refrigerant, which is suitable for very low tem‐

peratures (e.g. with a permissible fill capacity greater than

3.0 kg).

♦ Commercially available bottle adapter with seal (for connect‐

ing charge hose to recycling bottle, internal W 21.8 x 1/14 LH

left-hand thread and M 12 x 1.5-6G in accordance with SAE

J639)

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♦ Commercially available charge hose for R1234yf refrigerant

with seals (2m charge hose with external M12 x 1.5-6G thread

in accordance with SAE J639)

♦ Commercially available low-pressure service coupling in ac‐

cordance with SAE J639

Note

Dry ice evaporates at ambient temperature even from the insu‐

lated container (about 20 to 30% per day depending on the

ambient conditions). Therefore, only order the dry ice once all of

the necessary tools are ready and the measures can be per‐

formed immediately after receipt of the dry ice (e.g. do not order

the dry ice on a Friday if work is not going to be carried out at the

weekend).

CAUTION

Risk of frost-bite and suffocation from dry ice.

lk

Frost-bite on the skin and other body parts possible and risk of

suffocation in gaseous state.

– Wear protective gloves.

– Wear protective goggles.

– Only work with dry ice in well ventilated areas.

– Never work in or near cellars or other low lying areas.

CAUTION

Risk of explosion from incorrectly stored dry ice.

As dry ice evaporates, pressure builds up in the container. Un‐

suitable containers could burst.

– Only transport and store dry ice in dedicated containers.

Refilling refrigerant using a supercooled recycling cylinder

•

All requisite tools, equipment and a sufficient quantity of dry

ice ready

– Remove seal on recycling cylinder and unscrew sealing cap

from connection.

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Note

♦ Sealed recycling cylinders from your gas supplier usually

come pre-evacuated.

♦ Should the recycling cylinder not be evacuated, evacuate it as

necessary using a vacuum pump or an air conditioner service

station .

♦ Recycling cylinders are clearly marked as such and, unlike

refrigerant cylinders, do not have a non-return valve thereby

making them suitable for filling.

♦ Recycling cylinders are designed for international use, which

is why the “O” on the handwheel means “Open” (cylinder valve

= open) and not “0” (zero = closed).

♦ If an absolute pressure greater than 100 mbar but less than

900 mbar is measured in the recycling cylinder, evacuate the

recycling cylinder using a vacuum pump (or an air conditioner

service station ) (residual pressure less than 50 mbar)

⇒ “2.5 Evacuating refrigerant circuit”, page 140 .

♦ If an absolute pressure greater than 900 mbar is measured in

the recycling cylinder, this could be due to a number of rea‐

sons. The manual shut-off valve was opened and not closed

properly or the recycling cylinder had previously been used to

store refrigerant and then was not evacuated properly

⇒ “2.10 Emptying air conditioner service station”, page 154

(evacuate recycling cylinder). The recycling cylinder is leaking

(return the recycling cylinder to the supplier).

lk

– Connect a vacuum metre (or air conditioner service station )

to the recycling cylinder.

– Carefully open the manual shut-off valve of the recycling cyl‐

inder to check the vacuum and then check the vacuum in the

cylinder.

– If necessary, evacuate the recycling cylinder with the air con‐

ditioner service station .

Note

♦ Should there be any air trapped in the recycling cylinder, it can

be evacuated using an air conditioner service station for

R1234yf. To do this, unscrew the low pressure service cou‐

pling from the charge hose of the air conditioner service station

and connect the charge hose directly to the recycling cylinder

adapter for the extraction device (for R1234yf refrigerant) - dry

ice box .

♦ If air is trapped in the recycling cylinder and there is no air

conditioner service station for R1234yf available, the recycling

cylinder can also be evacuated with an air conditioner service

station for R134a using a relevant flushing container and

adapter -VAS 6338/38- along with the charge hose from ex‐

traction device (for R1234yf refrigerant) - dry ice box .

•

Residual pressure in the recycling cylinder less than 10 mbar

absolute pressure.

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Note

♦ Recycling cylinders are pre-evacuated by the supplier, though

it is not always possible to ensure that the vacuum will remain

intact in storage.

♦ To reliably determine the type and scope of the contamination

of the refilled refrigerant during analysis of the contaminated

refrigerant, the recycling cylinder must be evacuated before

refilling to a residual pressure less than 50 mbar.

– Switch off ignition.

– Ensure that the workplace is well ventilated. Switch on addi‐

tional workshop extraction systems if fitted.

– Connect the charge hose with a suitable adapter to the evac‐

uated recycling cylinder.

CAUTION

Risk of explosion from overfilling refrigerant reservoirs.

Refrigerant can expand and cause reservoirs to burst if they are

overfilled.

– Use a refrigerant tank with safety valve.

– Never exceed the permissible fill level of the refrigerant tank.

lk

Note

♦ Since contaminated refrigerant is only filled into a recycling

cylinder from a vehicle in the following work routine, there is

no danger of a recycling cylinder being overfilled with a fill vol‐

ume exceeding 3.0 kg.

♦ If contaminated refrigerant is filled into a recycling cylinder e.g.

from an air conditioner service station , measures must be

taken to ensure that the recycling cylinder is not overfilled due

to the larger volume. Use a recycling cylinder with an appro‐

priate permissible fill capacity and when refilling ensure by

means of weighing that the maximum permissible fill volume

is not exceeded.

CAUTION

Chemical reactions from contaminated refrigerant. Mixing

gases of unknown composition can cause different chemical

reactions.

Risk of injuries.

– Never mix together refrigerants of different origins.

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– Connect the service coupling for R1234yf refrigerant -5- to the

charge hose -4-.

– Connect the charge hose -4- with cylinder adapter -3- (and

seal -2-) to the recycling cylinder -1-.

– Place the spacer -6- in the insulated container -7-.

– Cover the base of the insulated container -7- with dry ice.

– Place the recycling cylinder -1- in the insulated container -7-

extraction device (for R1234yf refrigerant) - dry ice box .

– Pour the remainder of the dry ice in the insulated container

-7-.

– Cool down the recycling container -1- with dry ice (for approx.

15 minutes).

– Connect the recycling cylinder -1- via the service coupling

-5- to the connection of the air conditioner service station (or

the vehicle's refrigerant circuit).

– Open the manual shut-off valve of the recycling cylinder -1-.

Note

Recycling cylinders are designed for international use, which is

why the “O” on the handwheel means “Open” (cylinder valve =

open) and not “0” (zero = closed).

– Connect a pressure gauge to the refrigerant circuit (or use the

pressure gauge of the air conditioner service station ) and

check the pressure in the refrigerant circuit.

– Carefully open the service coupling -5- on the charge hose for

the recycling cylinder and allow the refrigerant to flow out

slowly into the recycling cylinder -1-.

– Wait until the refrigerant in the recycling cylinder -1- has liq‐

uefied (watch the display on the connected pressure gauge).

Note

♦ You can use your own pressure gauge or the pressure gauge

of the air conditioner service station to monitor the extraction

process.

♦ As soon as the displayed pressure is less than 0.3 bar after

approx. 60 minutes, it is safe to assume that the whole refrig‐

erant in the recycling cylinder is liquefied.

♦ Complete evaporation of the contaminated refrigerant from the

refrigerant circuit takes some time. After 60 minutes, it is safe

to assume that the whole refrigerant has evaporated.

– Close the service coupling -5- and manual shut-off valve of the

recycling cylinder -1-.

– Remove the charge hose -4- and cylinder connecting piece

-3- from the recycling cylinder -1- and close the recycling cyl‐

inder with the cap.

– The paperwork required for analysis, processing (or disposal)

of contaminated refrigerant must be filled in completely (dis‐

posal record, acceptance certificate etc.).

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Note

♦ All of the information and documents for analysis, processing

(or disposal) can be obtained from your gas processing / gas

disposal company.

♦ Included with the recycling cylinder is a form. Kindly fill this in

accordingly and attach it to the recycling cylinder.

♦ If it is not possible to weigh the recycling cylinder before and

after filling with contaminated refrigerant, the fill volume speci‐

fied for the vehicle in question can be quoted as the amount

of refrigerant that was filled in the recycling cylinder. This is

permissible as only the amount of refrigerant from a vehicle is

filled in a recycling cylinder.

– Move the insulated box -7- with recycling cylinder -1- and dry

ice to a secure, well ventilated area outside the building.

– Open the lid of the insulated box -7- or remove and allow the

dry ice to evaporate.

Note

Do not take the recycling cylinder -1- out of the insulated container

-7- until the dry ice has evaporated and the recycling cylinder has

adjusted to ambient temperature.

– Remove the recycling cylinder -1- from the insulated container

-7-.

lk

– Take the recycling cylinder -1- to a suitable location for storage

until it is ready to be collected by the gas processing / gas

disposal company.

– Evacuate the refrigerant circuit with the air conditioner service

station for at least 1 hour

⇒ “2.5 Evacuating refrigerant circuit”, page 140 .

Note

♦ Subsequent evacuation results in the last remnants of conta‐

minated refrigerant, which could still be in the refrigerant oil,

being removed at an absolute pressure of less than 10 mbar.

♦ The next steps depend on the complaint with the refrigerant

circuit

⇒ “2.3 Performing gas analysis of refrigerant”, page 134 .

– Fill out the data sheet for the recycling cylinder (R-cylinder) if

the refrigerant is contaminated and firmly attach it to the recy‐

cling cylinder -1-.

Note

In the “Other comments” section, details can be provided regard‐

ing e.g. who is to receive the analysis results and in which way.

Example for recycling cylinder (R-cylinder) data sheet

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Data sheet for R-cylinder if refrigerant is contaminated

Service contact

Dealership contact:

Email address:

Customer information:

Surname, first name:

Street:

Town/city:

Vehicle model

Identification

Vehicle identification

number:

Mileage:

Gas analysis performed

on:

Information about R-cylinder

Cylinder number:

Cylinder weight with

contents:

(gross weight)

Fill volume

(net weight)

lk

Other comments

2.14

Checking pressures

⇒ “2.14.1 General information on checking pressures in the re‐

frigerant circuit”, page 170

⇒ “2.14.2 Pressures and temperatures in refrigerant circuit”, page

173

⇒ “2.14.3 Checking pressures in the refrigerant circuit with the

ignition switched off”, page 176

⇒ “2.14.4 Checking pressures with air conditioning system switch‐

ed on - vehicles with mechanical air conditioning compressor”,

page 183 .

⇒ “2.14.5 Checking pressures with air conditioning system switch‐

ed on - vehicles with electrical air conditioning compressor”, page

205

2.14.1

General information on checking pres‐

sures in the refrigerant circuit

Note

Work on the refrigerant circuit that involves the air conditioner

service station can usually be carried out without the need to de-

energise the high-voltage system.

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Vehicles with electrically-actuated valves in the refrigerant circuit

that are not open when de-energised:

lk

Note

On vehicles with high-voltage system and auxiliary air condition‐

ing system functions (“heat pump mode” or “cooling of high-

voltage battery”), valves may be installed in the refrigerant circuit

that are not open when de-energised. These valves are opened

and closed e.g. via incremental motors and are no longer actu‐

ated when the ignition is switched off. To check the pressures in

the refrigerant circuit with the air conditioning system switched off,

however, no areas may be isolated, which is why these valves

must be opened before work is carried out ⇒ Heating, air condi‐

tioning; Rep. gr. 87 ; Refrigerant circuit; System overview -

refrigerant circuit and ⇒ Vehicle diagnostic tester in “Guided Fault

Finding” mode.

– Use the vehicle diagnostic tester to open the electrically-ac‐

tuated valves that are not open when de-energised ⇒ Vehicle

diagnostic tester in “Guided Fault Finding” mode.

All vehicles

NOTICE

Risk of damage to the air conditioner compressor or air condi‐

tioner service station.

Opening the valves with the air conditioning system switched

on can cause a short circuit between the high pressure and low

pressure side.

– Never open valves on the high pressure or low pressure side

with the air conditioning system switched on.

Note

♦ Certain conditions for testing are pertinent to a certain vehicle

and are described in the vehicle-specific workshop manual ⇒

Heating, air conditioning; Rep. gr. 00 ; Repair instructions;

Checking cooling output .

♦ Check the cooling output ⇒ Heating, air conditioning; Rep. gr.

00 ; Repair instructions; Checking cooling output (vehicle-spe‐

cific workshop manual).

♦ Connections with valve and service connections for measuring

and testing ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrig‐

erant circuit; System overview - refrigerant circuit (vehicle-

specific workshop manual)

♦ Depending on the version of air conditioner compressor, a

valve may be installed on the high-pressure side that prevents

liquefied refrigerant flowing back into the air conditioner com‐

pressor after the air conditioning system is switched off. If an

air conditioner compressor with this valve is installed in a ve‐

hicle with a refrigerant circuit with expansion valve, it could

take some time before the pressure on the high-pressure side

drops (the expansion valve is cold and the pressure on the

low-pressure side rises quickly after switching off, the expan‐

sion valve closes and refrigerant only flows slowly on the low-

pressure side). If the air conditioner compressor is switched

on, the pressure on the low-pressure side drops, the expan‐

sion valve opens and refrigerant can flow on the low-pressure

side.

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Under certain operating conditions, residual moisture in the re‐

frigerant circuit may lead to the formation of ice at the air condi‐

tioner compressor regulating valve. The ice impairs the air

conditioner compressor control and causes the evaporator to be

cooled excessively and to ice up. Icing-up of the evaporator may

give rise to the following problems:

♦ Repeated or sporadic failure of the air conditioner (no cooling/

heat output) after a lengthy journey. After switching off the en‐

gine and waiting for a short period, operation of air conditioner

returns to normal.

♦ Misting up of the windows on the inside after a long journey;

the windows are initially not cleared even by pressing the De-

frost button; the air conditioner functions properly again after

a short delay following engine shut-off (or after switching off

the air conditioner).

Remedy:

– On vehicles with an air conditioner compressor with air con‐

ditioner compressor regulating valve - N280- , check the

measured value of the evaporator output temperature sender

- G263- (via the “Read measured values” function). If the

measured value of the sender is too low under the operating

conditions described by the customer (at an ambient temper‐

ature above 0°C, colder than 0°C for an extended period even

though the -N280- is currently not actuated) or too high (higher

than approx. 10°C, even though the air conditioning system is

lk

functioning properly): the evaporator may ice up due to the

incorrect measured value ⇒ Vehicle diagnostic tester in “Gui‐

ded Fault Finding” mode - air conditioning system and ⇒

Heating, air conditioning; Rep. gr. 00 ; Repair instructions;

Checking cooling output (vehicle-specific workshop manual).

– On vehicles without evaporator output temperature sender -

G263- , use e.g. the footwell vent temperature sender - G192-

to check the outlet temperature with the temperature set to

“low” or “cold” for the driver and front passenger side with the

lowest setting (4 or 5 bars) for the fresh air blower speed, air

outlet in the footwell and fresh air mode under the operating

conditions described by the customer. If the measured value

of the sender is too low (with an ambient temperature higher

than 0°C, colder than 0°C for an extended period), the evap‐

orator could ice up due to the wrong measured value ⇒ Vehicle

diagnostic tester in “Guided Fault Finding” mode - air condi‐

tioning system.

– On vehicles with shut-off valves in the refrigerant circuit, check

the function and actuation of these valves ⇒ Vehicle diagnostic

tester in “Guided Fault Finding” mode - air conditioning sys‐

tem, ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant

circuit; System overview - refrigerant circuit and ⇒ Heating,

air conditioning; Rep. gr. 00 ; Repair instructions; Checking

cooling output (vehicle-specific workshop manual).

– Check the refrigerant line from the evaporator (or from the in‐

ner heat exchanger) and the air conditioner compressor (thick

pipe, low pressure side) with the engine running. If this line is

very icy when the complaint is encountered (a thin layer of ice

is acceptable), this is also evidence that the temperature in the

evaporator is too low ⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerant circuit; System overview - refrigerant circuit (vehi‐

cle-specific workshop manual).

– Empty the refrigerant circuit, renew the receiver with dryer,

renew the reservoir with dryer or desiccant cartridge and then

evacuate the refrigerant circuit for at least 3 hours ⇒ Heating,

air conditioning; Rep. gr. 87 ; Refrigerant circuit; System over‐

view - refrigerant circuit (vehicle-specific workshop manual)

and ⇒ page 129 .

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♦ ⇒ “2.14.3 Checking pressures in the refrigerant circuit with the

ignition switched off”, page 176

♦ ⇒ “2.14.4 Checking pressures with air conditioning system

switched on - vehicles with mechanical air conditioning com‐

pressor”, page 183 .

♦ ⇒ “2.14.5 Checking pressures with air conditioning system

switched on - vehicles with electrical air conditioning com‐

pressor”, page 205

2.14.2

Pressures and temperatures in refriger‐

ant circuit

General information about pressures and temperatures in the re‐

frigerant circuit ⇒ page 173

Pressures and temperatures in refrigerant circuit with expansion

valve ⇒ page 174

General information about pressures and temperatures in the re‐

frigerant circuit

♦ The pressures and temperatures in the refrigerant circuit de‐

pend on the current operating conditions (e.g. engine speed,

radiator running at level 1, 2, or 3, engine temperature, air

conditioner compressor actuation on or off) as well as envi‐

ronmental influences (e.g. ambient temperature, humidity, re‐

quired cooling output).

♦ On vehicles with air conditioner compressor regulating valve -

N280- , the pressure on the low pressure side is varied by

means of -N280- actuation.

lk

♦ For these reasons, the values given in the following table may

only be considered guidelines. They occur at an engine speed

of 1,500 to 2,000 rpm and an ambient temperature of 20°C

after about 20 minutes.

♦ Refer to the vehicle-specific refrigerant circuit for the pressure

gauge set measurement connections ⇒ Heating, air condi‐

tioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-specific work‐

shop manual).

♦ At 20°C and with the engine stationary, the refrigerant circuit

will adjust itself to a pressure of 4.7 bar overpressure

⇒ “6.1.3 Vapour pressure table for refrigerant”, page 17 (va‐

pour pressure table).

Note

♦ Pressure is indicated in various units: 1 MPa (Mega-Pascal)

is equal to 10 bar or 145 psi; 1 bar absolute pressure is equal

to 0 bar, which is about the same as ambient pressure (at‐

mospheric pressure).

♦ The pressures and temperatures in refrigerant circuits with re‐

strictor and reservoir are about the same as those in refriger‐

ant circuits with expansion valve. Since Volkswagen/Audi

currently only installs refrigerant circuits with expansion valve,

just this refrigerant circuit is described here.

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Pressures and temperatures in refrigerant circuit with expansion

valve

Note

♦ The following log (p), h-diagram (logarithmic pressure, energy

diagram) shows the processes that run during certain operat‐

ing conditions in the refrigerant circuit. These values change

depending on the environmental conditions (engine speed,

ambient temperature, requisite cooling output, etc.).

♦ The log (p), h-diagram shows the pressure (0 to 60 in bar ab‐

solute pressure) and the energy content (100 to 420, specific

enthalpy in kilojoules per kg of R1234yf refrigerant) in the re‐

frigerant circuit cycle.

lk

♦ The arrows indicate the direction of refrigerant flow in the re‐

frigerant circuit.

A - Area with vaporous refrigerant

B - Area with gaseous refrigerant

C - Area with liquefied refrigerant

D - Supercritical pressure and temperature range, physical state

of refrigerant undetermined (no longer a separation between liq‐

uefied and gaseous refrigerant)

1 - Low pressure side: output of inner heat exchanger, input of

air conditioner compressor, refrigerant is completely evapo‐

rated and gaseous, temperature of refrigerant is approx. -4°

C

2 - High pressure side: output of air conditioner compressor,

input of condenser, refrigerant has been compressed and is

gaseous, temperature of refrigerant is up to approx. 80°C

3 - High pressure side: output of condenser (receiver), input of

inner heat exchanger, refrigerant has been cooled down and

is liquefied, temperature of refrigerant is approx. 55°C

4 - High pressure side: output of inner heat exchanger, input of

expansion valve, liquefied refrigerant has cooled down fur‐

ther, temperature of refrigerant is approx. 50°C

5 - Low pressure side: expansion valve on evaporator side, in‐

put of evaporator, liquefied refrigerant comes to rest and

starts to evaporate, temperature of refrigerant approx. -7°C

6 - Low pressure side: output of evaporator, expansion valve,

input of inner heat exchanger, refrigerant mainly evapora‐

ted, small percentage is still vaporous, temperature of re‐

frigerant approx. -6°C

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Note

lk

♦ The temperatures given relate to the refrigerant in the refrig‐

erant circuit. The temperatures deviate from this on the sur‐

face of components containing refrigerant owing to heat

absorption and dissipation.

♦ The pressure and the temperature, too, are maintained at ap‐

prox. 3 bar absolute pressure (equates to approx. 2 bar over‐

pressure) in refrigerant circuits with regulated air conditioner

compressor despite thermal changes and different engine

speeds. This applies however only within the rated range of

the air conditioner compressor; if the rated range of the air

conditioner compressor is exceeded, the pressure will in‐

crease and so, too, will the temperature

⇒ “2.14 Checking pressures”, page 170 .

♦ On air conditioner compressors that do not regulate their per‐

formance themselves, the pressure on the low pressure side

and thereby the evaporator temperature are regulated by the

respective control via the air conditioner compressor regulat‐

ing valve - N280- . Depending on the version and the setting,

if an air temperature of less than approx. 2°C is measured after

the evaporator, the performance of the air conditioner com‐

pressor is lowered. At below 0°C, -N280- actuation is switched

off. This prevents the evaporator from cooling down too much

and becoming icy.

♦ On vehicles with two evaporators and two expansion valves,

the temperature and pressure in the refrigerant circuit are the

same at the second evaporator as those in vehicles with only

one evaporator and one expansion valve (parallel circuit).

♦ Depending on the version of refrigerant circuit, a component

with inner heat exchanger may be installed. In the internal heat

exchanger, the hot liquid refrigerant flowing on the high pres‐

sure side supplies energy to the cold gaseous or vaporous

refrigerant flowing on the low pressure side, thus enhancing

the efficiency of the air conditioner

⇒ “1.2.13 Refrigerant line with internal heat exchanger”, page

51 .

♦ Depending on the version of control unit (e.g. operating and

display unit for front air conditioning system - E87- or Clima‐

tronic control unit - J255- ), the measured ambient conditions

(exterior temperature, moisture in the passenger compartment

etc.) and the control unit setting (passenger compartment tem‐

perature, operating mode etc.), the pressure and thereby also

the temperature at the output of the evaporator can also be

regulated at a higher temperature ⇒ Vehicle diagnostic tester

in “Guided Fault Finding” mode - air conditioning system.

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2.14.3

Checking pressures in the refrigerant

circuit with the ignition switched off

Test prerequisites ⇒ page 176

Checking pressures with the ignition switched off ⇒ page 179

Conditions for testing

Note

♦ Work on the refrigerant circuit that involves the air conditioner

service station (checking the pressures in this case) can usu‐

ally be carried out without the need to de-energise the high-

voltage system.

♦ Only de-energise the high-voltage system if work on the high-

voltage system is necessary ⇒ page 3

All vehicles

Note

♦ Certain conditions for testing are pertinent to a certain vehicle

and are described in the vehicle-specific workshop manual ⇒ ^lk

Heating, air conditioning; Rep. gr. 00 ; Repair instructions;

Checking cooling output (vehicle-specific workshop manual).

♦ Depending on the version of air conditioner compressor, a

valve may be installed on the high-pressure side that prevents

liquefied refrigerant flowing back into the air conditioner com‐

pressor after the air conditioning system is switched off. If an

air conditioner compressor with this valve is installed in a ve‐

hicle with a refrigerant circuit with expansion valve, it could

take some time before the pressure on the high-pressure side

drops (the expansion valve is cold and the pressure on the

low-pressure side rises quickly after switching off, the expan‐

sion valve closes and refrigerant only flows slowly on the low-

pressure side). If the air conditioner compressor is switched

on, the pressure on the low-pressure side drops, the expan‐

sion valve opens and refrigerant can flow on the low-pressure

side.

♦ Check the cooling output ⇒ Heating, air conditioning; Rep. gr.

00 ; Repair instructions; Checking cooling output (vehicle-spe‐

cific workshop manual).

♦ Connections with valve and service connections for measuring

and testing ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrig‐

erant circuit (vehicle-specific workshop manual).

♦ Connect the air conditioner service station

⇒ “2.2 Connecting air conditioner service station to refrigerant

circuit”, page 131 .

Under certain operating conditions, residual moisture in the re‐

frigerant circuit may lead to the formation of ice at the air condi‐

tioner compressor regulating valve. The ice impairs the air

conditioner compressor control and causes the evaporator to be

cooled excessively and to ice up. Icing-up of the evaporator may

give rise to the following problems:

♦ Repeated or sporadic failure of the air conditioner (no cooling/

heat output) after a lengthy journey. After switching off the en‐

gine and waiting for a short period, operation of air conditioner

returns to normal.

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♦ Misting up of the windows on the inside after a long journey;

the windows are initially not cleared even by pressing the De-

frost button; the air conditioner functions properly again after

a short delay following engine shut-off (or after switching off

the air conditioner).

Remedy:

– On vehicles with an air conditioner compressor with air con‐

ditioner compressor regulating valve - N280- ,_lkcheck the

measured value of the evaporator output temperature sender

- G263- (via the “Read measured values” function). If the

measured value of the sender is too low under the operating

conditions described by the customer (at an ambient temper‐

ature above 0°C, colder than 0°C for an extended period even

though the -N280- is currently not actuated) or too high (higher

than approx. 10°C, even though the air conditioning system is

functioning properly): the evaporator may ice up due to incor‐

rect actuation of -N280- or the incorrect measured value of -

G263- ⇒ Vehicle diagnostic tester in “Guided Fault Finding”

mode - air conditioning system and ⇒ Heating, air condition‐

ing; Rep. gr. 00 ; Repair instructions; Checking cooling output

(vehicle-specific workshop manual).

– On vehicles without evaporator output temperature sender -

G263- , use e.g. the footwell vent temperature sender - G192-

to check the outlet temperature with the temperature set to

“low” or “cold” for the driver and front passenger side with the

lowest setting (4 or 5 bars) for the fresh air blower speed, air

outlet in the footwell and fresh air mode under the operating

conditions described by the customer. If the measured value

of the sender is too low (with an ambient temperature higher

than 0°C, colder than 0°C for an extended period), the evap‐

orator could ice up due to the wrong measured value ⇒ Vehicle

diagnostic tester in “Guided Fault Finding” mode - air condi‐

tioning system.

– On vehicles with shut-off valves in the refrigerant circuit, check

the function and actuation of these valves ⇒ Vehicle diagnostic

tester in “Guided Fault Finding” mode - air conditioning system

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit

(vehicle-specific workshop manual) and ⇒ Heating, air con‐

ditioning; Rep. gr. 00 ; Repair instructions; Checking cooling

output (vehicle-specific workshop manual).

– Check the refrigerant line from the evaporator (or from the in‐

ner heat exchanger) and the air conditioner compressor (thick

pipe, low pressure side) with the engine running. If this line is

very icy when the complaint is encountered (a thin layer of ice

is acceptable), this is also evidence that the temperature in the

evaporator is too low ⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerant circuit (vehicle-specific workshop manual).

– Empty the refrigerant circuit, renew all reservoirs/receivers

with dryer or desiccant cartridge and then evacuate the refrig‐

erant circuit for at least 3 hours ⇒ Heating, air conditioning;

Rep. gr. 87 ; Refrigerant circuit (vehicle-specific workshop

manual) and

⇒ “2 Working with air conditioner service station”, page 129 .

Conditions for testing

♦ Observe the general information on checking pressures in the

refrigerant circuit

⇒ “2.14.1 General information on checking pressures in the

refrigerant circuit”, page 170

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Note

All of the conditions for testing marked with * are pertinent to a

certain vehicle and are described in the vehicle-specific workshop

manual ⇒ Heating, air conditioning; Rep. gr. 00 ; Repair instruc‐

tions; Checking cooling output (vehicle-specific workshop man‐

ual).

General conditions for testing (these only have an influence on

the display of the pressure gauges during this measurement with

the air conditioning system switched on)

•

Radiator and condenser are clean (clean them if necessary).*

The heat insulation on the expansion valve is OK and properly

installed.*

•

The poly V-belt is OK and properly tensioned. The belts for air

conditioner compressor and alternator are in good condition

and correctly tensioned.*

The drive unit for the air conditioner compressor is OK and

properly installed.*

•

All air ducts, covers and seals are OK and properly installed.*

Diagnosis of the air conditioning system finds no faults (with

the engine running and the air conditioning system switched

on), no compressor deactivation conditions are shown in the

measured values (only on vehicles with diagnosis “air condi‐

tioning system”).* ⇒ Vehicle diagnostic tester in “Guided Fault

Finding” mode of air conditioning system.

•

The air flow rate through the dust and pollen filter is not im‐

paired by dirt.*

All dash panel air vents are open.*

lk

Note

♦ Depending on the engine, the air conditioner compressor is

driven by different components (belts or drive shaft). To pro‐

tect these components and the engine, the pulley or the air

conditioner compressor drive unit is fitted with an overload

protection which is tripped if the air conditioner compressor is

not operating smoothly ⇒ Heating, air conditioning; Rep. gr.

00 ; Repair instructions; Checking cooling output (vehicle-spe‐

cific workshop manual) and ⇒ Heating, air conditioning; Rep.

gr. 87 ; Air conditioner compressor (vehicle-specific workshop

manual).

♦ On certain versions, the radiator fan cuts in only after the pres‐

sure in the refrigerant circuit has exceeded a pre-set value

⇒ Vehicle diagnostic tester in “Guided Fault Finding” mode -

air conditioning system.

Other conditions for testing (these have an influence on the dis‐

play of the pressure gauge with this measurement)

•

The vehicle is not exposed to the sun's rays ⇒ Heating, air

conditioning; Rep. gr. 00 ; Repair instructions; Checking cool‐

ing output (vehicle-specific workshop manual).

•

Ambient temperature is above 15°C.

The ignition is switched off.

The air conditioner service station is connected to the refrig‐

erant circuit

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⇒ “2.2 Connecting air conditioner service station to refrigerant

circuit”, page 131 .

♦ ⇒ “2.14.4 Checking pressures with air conditioning system

switched on - vehicles with mechanical air conditioning com‐

pressor”, page 183 .

lk

♦ ⇒ “2.14.5 Checking pressures with air conditioning system

switched on - vehicles with electrical air conditioning com‐

pressor”, page 205

Checking pressures with the ignition switched off

Note

♦ The switching pressures for actuation of the air conditioner

compressor regulating valve - N280- , the air conditioning sys‐

tem magnetic clutch - N25- (if fitted) and the radiator fan (e.g.

radiator fan - V7- / radiator fan 2 - V177- ) are vehicle-specific

⇒ Vehicle diagnostic tester in “Guided Fault Finding” mode -

air conditioning system.

♦ The pressures must be measured at the service connections;

the fitting locations of these connections are vehicle-specific

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit

(vehicle-specific workshop manual).

♦ Once the planned measures are complete, separate the air

conditioner service station from the refrigerant circuit and

switch it off

⇒ “2.8 Switching off air conditioner service station and sepa‐

rating from refrigerant circuit”, page 151 .

•

The engine is at operating temperature (at an ambient tem‐

perature less than 25°C).

Note

♦ Should the engine not be at operating temperature, take the

vehicle for a short drive.

♦ To test the cooling output, the engine does not have to be at

operating temperature. However, to demand a certain cooling

output from the air conditioning system at an ambient temper‐

ature of less than 25°C, the engine is required to be warm if

ambient temperatures are low.

♦ Observe the test prerequisites ⇒ page 176 .

– On vehicles with high-voltage system, switch off “stationary air

conditioning” function (deactivate)⇒ Owner's Manual and ⇒

Operating instructions of infotainment / MMI .

– Switch off ignition.

– Connect the air conditioner service station

⇒ “2.2 Connecting air conditioner service station to refrigerant

circuit”, page 131 .

– Check the pressures in the refrigerant circuit with the engine

stationary.

– Take pressure readings from pressure gauges of air condi‐

tioner service station . Two results may be displayed:

♦ The pressure in the refrigerant circuit is lower than indicated

in the following table ⇒ page 182 .

♦ The pressure in the refrigerant circuit is equal to or greater than

that in the following table ⇒ page 183 .

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Note

♦ Vapour pressure table for R1234yf refrigerant

⇒ “6.1.3 Vapour pressure table for refrigerant”, page 17

♦ On vehicles with high-voltage system and auxiliary air condi‐

tioning system functions (“heat pump mode” or “cooling of

high-voltage battery”), valves may be installed in the refriger‐

ant circuit that are not open when de-energised. These valves

are opened and closed e.g. via incremental motors and are no

longer actuated when the ignition is switched off. Depending

lk

on the last operating status of the air conditioning system, cer‐

tain areas of the refrigerant circuit could be isolated by these

valves. Depending on the layout of the service connections in

the refrigerant circuit, these could be in an area that is isolated

(e.g. the area with the service connection on the high pressure

side). If necessary, these valves must be opened before the

pressure is tested ⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerant circuit (vehicle-specific workshop manual) and

⇒ Vehicle diagnostic tester in “Guided Fault Finding” mode.

♦ The pressures given in the table are slightly lower than speci‐

fied in the vapour pressure table for the R1234yf refrigerant.

The evaporation pressure of the refrigerant in the refrigerant

circuit is orientated around the coldest component and could

therefore also be slightly lower in a correctly charged refriger‐

ant circuit than that specified for the R1234yf refrigerant in the

vapour pressure table.

Ambient temperature (in de‐ Pressure in the refrigerant cir‐

grees C)

+15 °C

+20 °C

+25 °C

+30 °C

+35 °C

+40 °C

+45 °C

cuit in bar positive pressure

3.5

4.4

5.3

6.3

7.4

8.6

10.0

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Note

♦ The temperature of the components of the refrigerant circuit

should be the same as the ambient temperature. If individual

components of the refrigerant circuit are warmer or colder, the

pressure will deviate from the values shown in the tables.

♦ Absolute pressure means that 0 bar corresponds to an abso‐

lute vacuum. The normal ambient pressure corresponds to 1

bar absolute pressure. On most pressure gauges, a reading

of 0 bar corresponds to an absolute pressure of one bar (which

is confirmed by the existence of a -1 bar marking beneath the

0 scale marking).

♦ On vehicles with pressure senders ( high pressure sender -

G65- , pressure sender for refrigerant circuit - G805- or refrig‐

erant pressure and temperature sender - G395- , etc.) for

which the measured pressure is displayed in the measured

values of the diagnosis, the measured pressure should corre‐

late with the values in the table (or be slightly higher) ⇒ Vehicle

diagnostic tester in “Guided Fault Finding” mode - air condi‐

tioning system and ⇒ Heating, air conditioning; Rep. gr. 00 ;

Repair instructions; Checking cooling output (vehicle-specific

workshop manual).

lk

♦ The pressure is given in different units, 1 MPa (megapascal)

equates to 10 bar overpressure or 145 psi. At 0 bar overpres‐

sure, 1 bar absolute pressure is approximately the same as

ambient pressure (atmospheric pressure).

If the measured values are OK and there is no complaint:

– Unscrew (close) the handwheels of the quick-release coupling

adapters ⇒ Operating instructions air conditioner service sta‐

tion .

– Extract the refrigerant from the two charge hoses using the air

conditioner service station as instructed in the relevant oper‐

ating manual ⇒ Operating instructions air conditioner service

station .

– Switch off the air conditioner service station (and isolate it from

the power supply if necessary)

⇒ “2.8 Switching off air conditioner service station and sepa‐

rating from refrigerant circuit”, page 151 .

If the measured values are OK and there is complaint:

– Check the cooling output of the air conditioning system ⇒

Heating, air conditioning; Rep. gr. 00 ; Repair instructions;

Checking cooling output (vehicle-specific workshop manual)

and watch the pressures in the refrigerant circuit.

♦ ⇒ “2.14.4 Checking pressures with air conditioning system

switched on - vehicles with mechanical air conditioning com‐

pressor”, page 183 .

♦ ⇒ “2.14.5 Checking pressures with air conditioning system

switched on - vehicles with electrical air conditioning com‐

pressor”, page 205

If the measured values are not OK:

– Investigate the cause of the deviation and rectify.

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Note

♦ If the pressures are too low, it could be because there is too

little refrigerant in the circuit ⇒ Heating, air conditioning; Rep.

gr. 00 ; Technical data (vehicle-specific workshop manual)

and ⇒ “2.4 Emptying refrigerant circuit”, page 137 .

♦ If the pressures are too high, there may be too much refriger‐

ant or refrigerant oil in the circuit. Empty the refrigerant circuit

using the air conditioner service station

⇒ “2.4 Emptying refrigerant circuit”, page 137 . If the extracted

refrigerant volume is greater than the specified fill capacity for

the R1234yf refrigerant ⇒ Heating, air conditioning; Rep. gr.

00 ; Technical data (vehicle-specific workshop manual), evac‐

uate the refrigerant circuit and recharge with the correct

amount of R1234yf refrigerant. Then repeat the test. If the ex‐

tracted quantity of refrigerant roughly equates to the specified

fill capacity for the R1234yf refrigerant or is less, clean the re‐

frigerant circuit with refrigerant

lk

⇒ “1.6 Cleaning refrigerant circuit”, page 92 . Then add the

specified amount of refrigerant oil, evacuate the refrigerant

circuit, recharge with the correct volume of R1234yf refrigerant

and repeat the test.

♦ If the pressures are too low or too high and contaminated re‐

frigerant is found during the gas analysis, this may be the

cause of the deviation (different refrigerants have varying va‐

pour pressures). Empty the refrigerant circuit and then clean

with R1234yf refrigerant

⇒ “2.3 Performing gas analysis of refrigerant”, page 134 ,

⇒ “2.4 Emptying refrigerant circuit”, page 137 and

⇒ “1.6 Cleaning refrigerant circuit”, page 92

The pressure in the refrigerant circuit is lower than indicated in

the table

Too little refrigerant in circuit.

– Check for leaks in the refrigerant circuit

⇒ “1.4 Investigating leaks”, page 68 .

– Check the high pressure safety valve

⇒ “1.2.17 High-pressure safety valve”, page 53 .

If the high pressure safety valve has blown (check

⇒ “1.2.17 High-pressure safety valve”, page 53 ):

– Check radiator fan actuation or the radiator fan ⇒ Vehicle di‐

agnostic tester in “Guided Fault Finding” mode - air condition‐

ing system.

– On vehicles with shut-off valves for the refrigerant circuit,

check the actuation and function of these shut-off valves ⇒ Ve‐

hicle diagnostic tester in “Guided Fault Finding” mode - air

conditioning system (and battery control) and ⇒ Heating, air

conditioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-specific

workshop manual).

– Check refrigerant lines and refrigerant hoses for signs of

crushing (bottle-neck), external damage and tight bends ⇒

Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit (ve‐

hicle-specific workshop manual) and ⇒ Heating, air condi‐

tioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-specific

workshop manual).

– If no fault can be detected, clean the refrigerant circuit

⇒ “1.6 Cleaning refrigerant circuit”, page 92 .

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The pressure in the refrigerant circuit is equal to or greater than

that in the table

♦ ⇒ “2.14.4 Checking pressures with air conditioning system

switched on - vehicles with mechanical air conditioning com‐

pressor”, page 183 .

♦ ⇒ “2.14.5 Checking pressures with air conditioning system

switched on - vehicles with electrical air conditioning com‐

pressor”, page 205

2.14.4

Checking pressures with air condition‐

ing system switched on - vehicles with

mechanical air conditioning compressor

lk

Checking pressures ⇒ page 183

Specifications for pressures in the refrigerant circuit

⇒ page 187

Checking pressures

Refrigerant circuit with expansion valve, receiver with or without

air conditioning system magnetic clutch - N25- and air conditioner

compressor regulating valve - N280- (with externally regulated air

conditioner compressor)

Note

♦ Connect the air conditioner service station

⇒ “2.2 Connecting air conditioner service station to refrigerant

circuit”, page 131 .

♦ If on vehicles with two evaporators a problem is encountered

in just one evaporator, check the pressures in the refrigerant

circuit. If these are OK, check the line connection between the

evaporator that is causing the problem and the outlet of the

line connection at the distribution point of the refrigerant lines

(for bottle-neck or blockage). If no fault can be determined,

empty the refrigerant circuit and recharge with the prescribed

amount of refrigerant. Then check the pressures and the cool‐

ing output of the air conditioner again. If the problem persists,

replace the expansion valve upstream of the problematic

evaporator ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrig‐

erant circuit (vehicle-specific workshop manual).

♦ ⇒ “2.14.3 Checking pressures in the refrigerant circuit with the

ignition switched off”, page 176

Conditions for testing

•

The air conditioner service station is connected to the refrig‐

erant circuit

⇒ “2.2 Connecting air conditioner service station to refrigerant

circuit”, page 131 .

•

Observe the conditions for testing pressures in the refrigerant

circuit with the ignition switched off ⇒ page 176 .

The pressures in the refrigerant circuit comply with the speci‐

fications with the ignition switched off

⇒ “2.14.3 Checking pressures in the refrigerant circuit with the

ignition switched off”, page 176 .

•

Observe the conditions for testing the cooling output ⇒ Heat‐

ing, air conditioning; Rep. gr. 00 ; Repair instructions; Check‐

ing cooling output (vehicle-specific workshop manual).

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

Note

♦ The switching pressures for actuation of the air conditioner

compressor regulating valve - N280- , the air conditioning sys‐

tem magnetic clutch - N25- (if fitted) and the radiator fan - V7-

are vehicle-specific ⇒ Vehicle diagnostic tester in “Guided

Fault Finding” mode - air conditioning system.

♦ The pressures must be measured at the service connections;

the fitting locations of these connections are vehicle-specific

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit

(vehicle-specific workshop manual).

•

The engine is at operating temperature (at an ambient tem‐

perature less than 25°C).

Note

♦ Should the engine not be at operating temperature, take the

vehicle for a short drive.

♦ To test the cooling output, the engine does not have to be at

operating temperature. However, to demand a certain cooling

output from the air conditioning system at an ambient temper‐

ature of less than 25°C, the engine is required to be warm if

ambient temperatures are low.

lk

– Start engine.

– Set the air conditioning system to maximum cooling output ⇒

Heating, air conditioning; Rep. gr. 00 ; Repair instructions;

Checking cooling output (vehicle-specific workshop manual).

•

The air conditioner compressor is actually driven with the en‐

gine running (visual check ⇒ Heating, air conditioning; Rep.

gr. 87 ; Refrigerant circuit (vehicle-specific workshop man‐

ual)).

•

The air conditioner compressor regulating valve - N280- is ac‐

tuated ⇒ Vehicle diagnostic tester in “Guided Fault Finding”

mode - air conditioning system.

Note

♦ Depending on the engine, the air conditioner compressor is

driven by different components (belts or drive shaft). To pro‐

tect these components and the engine, the pulley or the air

conditioner compressor drive unit is fitted with an overload

protection which is tripped if the air conditioner compressor is

not operating smoothly ⇒ Heating, air conditioning; Rep. gr.

87 ; Air conditioner compressor (vehicle-specific workshop

manual).

♦ On vehicles with air conditioner compressor regulating valve -

N280- , the control current can be gleaned from the measured

values ⇒ Vehicle diagnostic tester in “Guided Fault Finding”

mode - air conditioning system.

If the air conditioner compressor is not driven or the regulating

valve not activated when the engine is running:

– Determine the cause, e.g. by interrogating the event memory

of the air conditioning system, and rectify it ⇒ Vehicle diag‐

nostic tester in “Guided Fault Finding” mode - air conditioning

system.

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– If fitted, check the voltage supply for the air conditioning sys‐

tem magnetic clutch - N25- . If this is OK, repair the magnetic

clutch ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant

circuit (vehicle-specific workshop manual).

– Check actuation of the air conditioner compressor regulating

valve - N280- ⇒ Vehicle diagnostic tester in “Guided Fault

Finding” mode - air conditioning system.

lk

Note

♦ On air conditioner compressors with an air conditioning sys‐

tem magnetic clutch - N25- , the air conditioner compressor

only works (delivers refrigerant) if in addition to the air condi‐

tioner compressor regulating valve - N280- , -N25- is actuated

⇒ Vehicle diagnostic tester in “Guided Fault Finding” mode -

air conditioning system.

♦ -N280- (and -N25- ) is actuated by the air conditioning system

control unit - J301- , the operating and display unit for front air

conditioning system - E87- and the Climatronic control unit -

J255- or a downstream control unit ⇒ Vehicle diagnostic tester

in “Guided Fault Finding” mode - air conditioning system and

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit

(vehicle-specific workshop manual).

♦ All of the conditions for testing marked with * are pertinent to

a certain vehicle and are described in the vehicle-specific

workshop manual ⇒ Heating, air conditioning; Rep. gr. 00 ;

Repair instructions (vehicle-specific workshop manual) and ⇒

Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit (ve‐

hicle-specific workshop manual).

•

The radiator and condenser are clean (clean if necessary) * ⇒

Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit (ve‐

hicle-specific workshop manual).

The heat insulation on the expansion valve is OK and mounted

correctly * ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrig‐

erant circuit (vehicle-specific workshop manual).

The poly V-belt is OK and properly tensioned. The belts for air

conditioner compressor and alternator are in good condition

and correctly tensioned.* ⇒ Heating, air conditioning system;

Rep. gr. 87 ; Air conditioner compressor (vehicle-specific

workshop manual) and ⇒ Heating, air conditioning system;

Rep. gr. 87 ; Refrigerant circuit (vehicle-specific workshop

manual).

•

The drive unit for the air conditioner compressor is OK and

mounted properly * ⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerant circuit (vehicle-specific workshop manual) and ⇒

Heating, air conditioning; Rep. gr. 87 ; Air conditioner com‐

pressor (vehicle-specific workshop manual).

•

The air ducts, covers and seals are OK and mounted correctly

* ⇒ Heating, air conditioning; Rep. gr. 87 ; Overview of fitting

locations - air conditioning system (vehicle-specific workshop

manual).

Diagnosis of the air conditioning system finds no faults (with

the engine running and the air conditioning system switched

on), no compressor deactivation conditions are shown in the

measured values of the respective control unit (only on vehi‐

cles with diagnosis “air conditioning system”).* ⇒ Vehicle di‐

agnostic tester in “Guided Fault Finding” mode of air

conditioning system.

•

The air flow rate through the dust and pollen filter is not im‐

paired by dirt.* ⇒ Heating, air conditioning system; Rep. gr.

2. Working with air conditioner service station

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

87 ; Overview of fitting locations - air conditioning system (ve‐

hicle-specific workshop manual).

•

The heater and air conditioner does not draw any secondary

air at highest fresh air blower speed. The evaporator and heat‐

er are not drawing in secondary air at the highest fresh air

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blower speed * ⇒ Heating, air conditioning; Rep. gr. 87 ;

Overview of fitting locations - air conditioning system (vehicle-

specific workshop manual).

The air flaps in the heating and air conditioning unit, in the

heating and in the evaporator reach their end position * ⇒

Heating, air conditioning; Rep. gr. 00 ; Repair instructions;

Checking cooling output (vehicle-specific workshop manual)

and ⇒ Heating, air conditioning; Rep. gr. 87 ; Overview of

fitting locations - air conditioning system (vehicle-specific

workshop manual).

•

The fresh air intake ducts under the bonnet and in the pas‐

senger compartment and the corresponding water drain

valves are OK * ⇒ Heating, air conditioning; Rep. gr. 00 ;

Repair instructions; Checking cooling output (vehicle-specific

workshop manual) and ⇒ Heating, air conditioning; Rep. gr.

87 ; Overview of fitting locations - air conditioning system (ve‐

hicle-specific workshop manual).

•

Engine warm.

The vehicle is not exposed to the sun's rays ⇒ Heating, air

conditioning; Rep. gr. 00 ; Repair instructions; Checking cool‐

ing output (vehicle-specific workshop manual).

•

Ambient temperature is above 15°C.

All dash panel diffusers are open * ⇒ Heating, air conditioning;

Rep. gr. 87 ; Air duct system (vehicle-specific workshop man‐

ual).

Setting e.g. on operating and display unit for front air conditioning

system - E87- and Climatronic control unit - J255- or air condi‐

tioning system control unit - J301- (and operating and display unit

for rear Climatronic - E265- on vehicles with two heating and air

conditioning units) * ⇒ Heating, air conditioning; Rep. gr. 00 ;

Repair instructions; Checking cooling output (vehicle-specific

workshop manual) and ⇒ Heating, air conditioning; Rep. gr. 87 ;

Overview of fitting locations - air conditioning system (vehicle-

specific workshop manual).

Setting on -E87- / -J255- *: ⇒ Heating, air conditioning; Rep. gr.

00 ; Repair instructions; Checking cooling output (vehicle-specific

workshop manual) and ⇒ Heating, air conditioning; Rep. gr. 87 ;

Overview of fitting locations - air conditioning system (vehicle-

specific workshop manual).

– Select “Auto” mode (air conditioner compressor switched on).

– Set temperature to “cold” or “LO” for the driver and front pas‐

senger side (and the rear on the left and right in vehicles with

two heating and air conditioning units).

Setting on -J301- *:

– Press A/C button and Rec or recirculate buttons.

– Turn rotary temperature knob in direction of “cold” stop.

– Set rotary fresh air blower switch to “4” (maximum fresh air

blower speed).

The following conditions for testing should then be met in the sys‐

tem:

•

The radiator fan - V7- is running or the radiator fan - V7- and

radiator fan 2 - V177- are running (at least stage 1) * ⇒ Heat‐

ing, air conditioning; Rep. gr. 00 ; Repair instructions; Check‐

186

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

ing cooling output (vehicle-specific workshop manual) and ⇒

Heating, air conditioning; Rep. gr. 87 ; Overview of fitting lo‐

cations - air conditioning system (vehicle-specific workshop

manual).

Note

On certain versions, the radiator fan cuts in only after the pressure

in the refrigerant circuit has exceeded a pre-set value ⇒ Vehicle

diagnostic tester in “Guided Fault Finding” mode - air conditioning

system.

lk

•

The fresh air blower - V2- (and the rear fresh air blower - V80-

on vehicles with two heating and air conditioning units) is

running at maximum speed.*

•

The coolant shut-off valve is closed * ⇒ Heating, air condi‐

tioning; Rep. gr. 00 ; Repair instructions; Checking cooling

output (vehicle-specific workshop manual) and ⇒ Heating, air

conditioning; Rep. gr. 87 ; Overview of fitting locations - air

conditioning system (vehicle-specific workshop manual).

•

The valves of the pump-valve unit are closed and the coolant

circulation pump is not delivering * ⇒ Heating, air conditioning;

Rep. gr. 00 ; Repair instructions; Checking cooling output

(vehicle-specific workshop manual) and ⇒ Heating, air con‐

ditioning; Rep. gr. 87 ; Overview of fitting locations - air

conditioning system (vehicle-specific workshop manual).

•

The fresh air blower - V2- (and the rear fresh air blower - V80-

on vehicles with two heating and air conditioning units) is

running at maximum speed.*

The air recirculation flap/fresh air flap is in “recirculation

mode” (within 1 minute after starting the vehicle, the air flow

flap closes and the air recirculation flap opens).*

•

The coolant shut-off valve is closed.*

The valves for the pump-valve unit are closed and the coolant

circulation pump is not delivering.*

Specifications for pressures in the refrigerant circuit

♦ Observe the conditions for testing and the pressures

⇒ page 183 .

Testing:

– Raise engine speed to 2000 rpm.

– Observe pressure display (e.g. pressure gauge) of air condi‐

tioner service station ⇒ Operating instructions of air condi‐

tioner service station .

Note

♦ The switching pressures for actuation of the air conditioner

compressor regulating valve - N280- and the radiator fan are

vehicle-specific ⇒ Vehicle diagnostic tester in “Guided Fault

Finding” mode - air conditioning system.

♦ The pressures must be measured at the service connections;

the fitting locations of these connections are vehicle-specific

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit

(vehicle-specific workshop manual).

2. Working with air conditioner service station

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

High-pressure side:

Rising from starting pressure (when pressure gauge is connec‐

ted) to maximum 20 bar.

Low-pressure side:

From the output pressure (when connecting the pressure gauge)

dropping to a value of between 1.5 and 2.3 bar absolute pressure

(depending on required cooling output).

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lk

Note

♦ In the event of a very high cooling output (e.g. at high outside

temperatures and high fresh air blower speed while the engine

is running slowly), the air conditioner compressor is initially

incapable of changing the pressure on the low pressure side

to the specified level (e.g. for a certain period after switching

on the air conditioning system). The air conditioner compres‐

sor is actuated with the maximum specified control current.

However, the delivery volume of the air conditioner compres‐

sor is not enough under these operating conditions and at this

engine speed to lower the pressure on the low pressure side

to the specification. One way of checking the regulating be‐

haviour of the air conditioner compressor under these condi‐

tions is to actuate e.g. the fresh air blower with only approx.

40% of the maximum voltage and to check the pressures at

reduced fresh air blower speed ⇒ Vehicle diagnostic tester in

“Guided Fault Finding” mode - air conditioning system and ⇒

Heating, air conditioning; Rep. gr. 00 ; Repair information;

Checking cooling output (vehicle-specific workshop manual).

♦ If the demand on the cooling output is low (e.g. at an ambient

temperature of 20°C and a low fresh air blower speed), pres‐

sure on the high pressure side may only increase up to a value

of 6 to 7 bar (the energy exchange is low, the refrigerant is

cooled down quickly in the condenser). To check the regulat‐

ing behaviour and the pressures in the refrigerant circuit under

these conditions, e.g. actuate the fresh air blower with maxi‐

mum voltage, set the air conditioning system to maximum

heating output and activate air recirculation ⇒ Vehicle diag‐

nostic tester in “Guided Fault Finding” mode - air conditioning

system and ⇒ Heating, air conditioning; Rep. gr. 00 ; Repair

instructions; Checking cooling output (vehicle-specific work‐

shop manual).

♦ Under unfavourable conditions (very high ambient tempera‐

tures, high atmospheric humidity), the pressure on the high

pressure side can increase to a maximum of 29 bar.

♦ The specified working current for the air conditioner compres‐

sor regulating valve - N280- is displayed as a measured value

by the operating and display unit for front air conditioning sys‐

tem - E87- , the air conditioning system control unit - J301- and

the Climatronic control unit - J255- ⇒ Vehicle diagnostic tester

in “Guided Fault Finding” mode - air conditioning system.

♦ The high pressure measured by the high pressure sender -

G65- , the pressure sender for refrigerant circuit - G805- and

the refrigerant pressure and temperature sender - G395- is

displayed as a measured value by -E87- , -J301- or -J255-

⇒ Vehicle diagnostic tester in “Guided Fault Finding” mode -

air conditioning system.

♦ The low pressure adjusts depending on the control current for

the air conditioner compressor regulating valve - N280- and

the control characteristic of the expansion valve within the

performance band of the air conditioner compressor in the tol‐

erance range ⇒ Vehicle diagnostic tester in “Guided Fault

Finding” mode - air conditioning system.

♦ In unfavourable conditions (very high ambient temperatures,

high air humidity), the performance of the air conditioner com‐

pressor may not always be enough to reach the specified

pressure value within the given time (it could take slightly lon‐

ger, depending on the engine speed, for the prescribed low

pressure to be reached).

2. Working with air conditioner service station

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

♦ If the air conditioner compressor's capacity utilisation is above

90%, pressure on the low pressure side could be higher than

the specified tolerance range. The air conditioner compressor

output is no longer sufficient in the prevailing conditions (am‐

bient temperature, air humidity, setting of the air conditioning

system, engine speed, etc.) to change the pressure on the low

pressure side to approx. 2 bar.

♦ The specified working current for the air conditioner compres‐

sor regulating valve - N280- must be higher than 0.3 A so that

-N280- can be actuated reliably ⇒ Vehicle diagnostic tester in

“Guided Fault Finding” mode - air conditioning system.

♦ When setting to “maximum cooling output”, the control current

for the air conditioner compressor regulating valve - N280- is

regulated at approx. 0.65 A (to 0.85 A). This measured value

is vehicle-specific and is displayed in the ⇒ Vehicle diagnostic

tester in “Guided Fault Finding” mode - air conditioning sys‐

tem.

♦ Absolute pressure means that 0 bar corresponds to an abso‐

lute vacuum. The normal ambient pressure corresponds to 1

bar absolute. On most pressure gauges, a reading of 0 bar

corresponds to an absolute pressure of 1 bar (which is con‐

firmed by the existence of a -1 bar marking beneath the 0 scale

marking). Depending on the respective control unit version,

pressure can be displayed as a measured value based on ab‐

solute or relative pressure (difference between displays 1 bar)

⇒ Vehicle diagnostic tester in “Guided Fault Finding” mode -

air conditioning system and ⇒ Heating, air conditioning; Rep.

gr. 00 ; Repair instructions; Checking cooling output (vehicle-

specific workshop manual).

♦ The temperature of the air after the evaporator, the current air

conditioner compressor speed and the pressure of the refrig‐

erant on the high pressure side along with the specified work‐

ing current for the air conditioner compressor regulating valve

- N280- are displayed e.g. as a measured value by the oper‐

ating and display unit, the Climatronic control unit - J255-

⇒ Vehicle diagnostic tester in “Guided Fault Finding” mode -

air conditioning system.

Possible deviations from specification,

cause and rectification

♦ The required cooling output is not

reached.

⇒ page 192

♦ High pressure remains constant or in‐

creases only slightly (above the pressure

measured when the engine is station‐

ary).

♦ Low pressure drops quickly to the spec‐

ification or lower.

♦ The required cooling output is not

reached.

⇒ page 193

♦ The high pressure equates to the speci‐

fication

♦ The low pressure equates to the specifi‐

cation or is too low

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Possible deviations from specification,

cause and rectification

♦ The requisite cooling output is not

reached.

⇒ page 194

⇒ page 195

♦ High pressure does not increase or only

marginally above the pressure with the

engine stationary

♦ The low pressure does not drop or only

marginally

♦ The requisite cooling output is not

reached.

♦ The high pressure increases beyond the

specified value

♦ Low pressure drops quickly to the spec‐

ification or lower.

♦ The requisite cooling output is reached ⇒ page 196

initially but after a while or after an ex‐

tended period, the cooling output is no

longer sufficient.

lk

♦ The high pressure and the low pressure

are normal to start with

♦ After some time, the high pressure rises

above the specification, the low pressure

still equates to the specification or it

drops below the specification.

♦ The requisite cooling output is reached ⇒ page 198

initially but after a short or extended pe‐

riod, the required level is no longer

reached.

♦ The high pressure and low pressure are

normal to start with but after a while, the

high pressure rises above the specifica‐

tion and the low pressure drops to the

specification or lower.

♦ The high pressure and low pressure are

normal to start with. After a while, the low

pressure drops to the specification or

lower and the evaporator ices up.

♦ The requisite cooling output is reached. ⇒ page 199

♦ The high pressure equates to the speci‐

fication

♦ The low pressure is too low (lower than

the specification)

♦ The air conditioner compressor is noisy ⇒ page 201

(especially immediately after being

switched on),

♦ The requisite cooling output is reached.

♦ High pressure normal or too high

♦ The low pressure is normal or too high

(the specification is not always reached)

2. Working with air conditioner service station

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Possible deviations from specification,

cause and rectification

lk

♦ The required cooling output is not

reached.

⇒ page 203

♦ The high pressure and low pressure

equate to the specification

Possible deviation from specification during pressure test

♦ The required cooling output is not reached.

♦ High pressure remains constant or increases only slightly (above the pressure measured when the engine

is stationary).

♦ The low pressure does not drop or only marginally

Possible causes for deviation from specification and rectification

♦ Actuation of the air conditioner compressor regulating valve - N280- is defective.

– Check actuation of the air conditioner compressor regulating valve - N280- and repair if necessary ⇒ Vehicle

diagnostic tester in “Guided Fault Finding” mode - air conditioning system.

♦ Air conditioner compressor regulating valve - N280- or air conditioner compressor defective

– Check function of -N280- ; if necessary remove -N280- and check for dirt ⇒ Vehicle diagnostic tester in

“Guided Fault Finding” mode - air conditioning system and ⇒ page 79

– -N280- or renew the air conditioner compressor ⇒ page 79

– If dirt is found in the refrigerant circuit, clean the refrigerant circuit (flush with R1234yf refrigerant) and renew

the expansion valve and desiccant bag/desiccant cartridge (or renew the receiver/reservoir) ⇒ page 79 and

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-specific workshop manual) as well as

⇒ “1.6 Cleaning refrigerant circuit”, page 92 .

Final measures

– Recharge the refrigerant circuit ⇒ “2.6 Charging refrigerant circuit”, page 146

– Repeat the test

⇒ “2.14.4 Checking pressures with air conditioning system switched on - vehicles with mechanical air

conditioning compressor”, page 183

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Note

♦ If this problem is encountered, ensure that the air conditioner

compressor (air conditioner compressor shaft) is actually be‐

ing driven via the pulley/drive unit ⇒ Heating, air conditioning;

Rep. gr. 87 ; Refrigerant circuit (vehicle-specific workshop

manual) and ⇒ Heating, air conditioning; Rep. gr. 87 ; Re‐

frigerant circuit (vehicle-specific workshop manual).

♦ If no fault can be found for this complaint, clean the refrigerant

circuit (flush with R1234yf refrigerant)

⇒ “1.6 Cleaning refrigerant circuit”, page 92 .

♦ Check the measured values of the evaporator output temper‐

ature sender - G263- and actuation of -N280- . If the measured

value of -G263- is faulty, the evaporator could ice up or the

cooling output may not be reached ⇒ Vehicle diagnostic tester

in “Guided Fault Finding” mode - air conditioning system.

♦ If, after repeating the test when the expansion valve has been

renewed, the air conditioning system is not operating correctly,

clean the refrigerant circuit (flush with R1234yf refrigerant)

⇒ “1.6 Cleaning refrigerant circuit”, page 92 . Then renew the

air conditioner compressor and desiccant insert/desiccant car‐

tridge (or reservoir/receiver) ⇒ Heating, air conditioning; Rep.

gr. 87 ; Refrigerant circuit (vehicle-specific workshop manual).

♦ In this case, the evaporator may ice up even though the correct

volume of refrigerant is present in the refrigerant circuit.

♦ If the expansion valve is defective (always closed or not open‐

ing wide enough), -N280- will change to maximum power and

the low pressure will fall to the diagram value or less (the air

conditioner compressor is drawing the refrigerant out of the

low pressure side) ⇒ Vehicle diagnostic tester in “Guided Fault

Finding” mode - air conditioning system. However, since no

refrigerant can flow through the expansion valve, the required

cooling output is not reached, the high pressure may also not

rise or only marginally since no energy exchange is taking

place.

lk

Possible deviation from specification during pressure test

♦ The required cooling output is not reached.

♦ The high pressure equates to the specification

♦ The low pressure equates to the specification or is too low

Possible causes for deviation from specification and rectification

♦ There is too little refrigerant in the refrigerant circuit.

♦ The expansion valve is defective.

– Extract refrigerant from the refrigerant circuit ⇒ “2.4 Emptying refrigerant circuit”, page 137 .

– If the extracted refrigerant volume is considerably less than the specified fill volume (more than 100 g less)

⇒ Heating, air conditioning; Rep. gr. 00 ; Technical data (vehicle-specific workshop manual), search for

the leak and rectify the cause ⇒ “1.4 Investigating leaks”, page 68

– The extracted refrigerant volume approximately equates to the prescribed fill volume, renew the expansion

valve for the evaporator in the heater and air conditioning unit ⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerant circuit (vehicle-specific workshop manual)

Final measures

2. Working with air conditioner service station

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lk

Possible deviation from specification during pressure test

– Recharge the refrigerant circuit ⇒ “2.6 Charging refrigerant circuit”, page 146

– Repeat the test

⇒ “2.14.4 Checking pressures with air conditioning system switched on - vehicles with mechanical air

conditioning compressor”, page 183

Note

♦ Check the measured values of the evaporator output temper‐

ature sender - G263- and actuation of -N280- . If the measured

value of -G263- is faulty, the evaporator could ice up or the

cooling output may not be reached ⇒ Vehicle diagnostic tester

in “Guided Fault Finding” mode - air conditioning system.

♦ If, after repeating the test when the expansion valve has been

renewed, the air conditioning system is not operating correctly,

clean the refrigerant circuit (flush with R1234yf refrigerant)

⇒ “1.6 Cleaning refrigerant circuit”, page 92 . Then renew the

air conditioner compressor and reservoir/receiver (or desic‐

cant cartridge) ⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerant circuit (vehicle-specific workshop manual).

Possible deviation from specification during pressure test

♦ The requisite cooling output is not reached.

♦ High pressure does not increase or only marginally above the pressure with the engine stationary

♦ The low pressure does not drop or only marginally

Possible causes for deviation from specification and rectification

♦ The air conditioner compressor is not driven or not driven at the specified speed

– Check the drive of the air conditioner compressor (via belts or drive unit) ⇒ Heating, air conditioning; Rep.

gr. 87 ; Air conditioner compressor (vehicle-specific workshop manual).

♦ Actuation of the air conditioner compressor regulating valve - N280- (the air conditioning system magnetic

clutch - N25- ) is defective.

– Check actuation of the air conditioner compressor regulating valve - N280- (and the air conditioning system

magnetic clutch - N25- ) and repair if necessary ⇒ Vehicle diagnostic tester in “Guided Fault Finding” mode

- air conditioning system.

♦ Air conditioner compressor regulating valve - N280- or air conditioner compressor defective

– Check function of -N280- ; if necessary remove -N280- and check for dirt ⇒ Vehicle diagnostic tester in

“Guided Fault Finding” mode - air conditioning system and ⇒ page 79

– -N280- or renew the air conditioner compressor ⇒ page 79

– If dirt is found in the refrigerant circuit, clean the refrigerant circuit (flush with R1234yf refrigerant) and renew

the expansion valve and desiccant bag/desiccant cartridge (or renew the receiver/reservoir) ⇒ page 79 ,

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-specific workshop manual) and

⇒ “1.6 Cleaning refrigerant circuit”, page 92 .

♦ Bottle-neck or blockage in refrigerant circuit (e.g. in refrigerant line between service connection on “low

pressure side” and air conditioner compressor).

– Touch the refrigerant circuit by hand to feel for a drop in temperature ⇒ Heating, air conditioning; Rep. gr.

87 ; Refrigerant circuit (vehicle-specific workshop manual). If a drop in temperature is felt on a component,

if there is a kink or bottle-neck in the hose or pipeline, renew this component. In the event of a blockage or

if no fault can be found, clean the refrigerant circuit (flush with R1234yf refrigerant)

⇒ “1.6 Cleaning refrigerant circuit”, page 92

– Renew the expansion valve and desiccant bag/desiccant cartridge (or reservoir/receiver) ⇒ page 79 and

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-specific workshop manual).

Final measures

194

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

Possible deviation from specification during pressure test

– Recharge the refrigerant circuit ⇒ “2.6 Charging refrigerant circuit”, page 146

– Repeat the test

⇒ “2.14.4 Checking pressures with air conditioning system switched on - vehicles with mechanical air

conditioning compressor”, page 183

Note

♦ If this problem is encountered, ensure that the air conditioner

compressor (air conditioner compressor shaft) is actually be‐

ing driven via the pulley / drive unit (take note of overload

safety device) ⇒ Heating, air conditioning; Rep. gr. 87 ; Re‐

frigerant circuit (vehicle-specific workshop manual).

♦ On certain engines, air conditioner compressors are used that

feature in addition to -N280- an air conditioning system mag‐

netic clutch - N25- on the belt pulley. In the event of this

problem, make sure that -N25- is actually being actuated and

that the air conditioner compressor (air conditioner compres‐

sor shaft) is being driven by the pulley ⇒ Heating, air condi‐

tioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-specific

workshop manual) and ⇒ Electronic parts catalogue .

♦ If no fault can be found for this complaint, clean the refrigerant

circuit (flush with R1234yf refrigerant)

⇒ “1.6 Cleaning refrigerant circuit”, page 92 .

lk

♦ Check the measured values of the evaporator output temper‐

ature sender - G263- and actuation of -N280- . If the measured

value of -G263- is faulty, the evaporator could ice up or the

cooling output may not be reached ⇒ Vehicle diagnostic tester

in “Guided Fault Finding” mode - air conditioning system.

♦ If, after repeating the test when the expansion valve has been

renewed, the air conditioning system is not operating correctly,

clean the refrigerant circuit (flush with R1234yf refrigerant)

⇒ “1.6 Cleaning refrigerant circuit”, page 92 . Then renew the

air conditioner compressor and reservoir/receiver (or desic‐

cant cartridge) ⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerant circuit (vehicle-specific workshop manual).

♦ If the expansion valve is defective (always closed or not open‐

ing wide enough), -N280- will change to maximum power and

the low pressure will fall to the diagram value or less (the air

conditioner compressor is drawing the refrigerant out of the

low pressure side) ⇒ Vehicle diagnostic tester in “Guided Fault

Finding” mode - air conditioning system. However, since no

refrigerant can flow through the expansion valve, the required

cooling output is not reached, the high pressure may also not

rise or only marginally since no energy exchange is taking

place.

Possible deviation from specification during pressure test

♦ The requisite cooling output is not reached.

♦ The high pressure increases beyond the specified value

♦ Low pressure drops quickly to the specification or lower.

Possible causes for deviation from specification and rectification

2. Working with air conditioner service station

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

Possible deviation from specification during pressure test

♦ Actuation of the air conditioner compressor regulating valve - N280- is defective.

– Check the actuation of -N280- and, if necessary, repair ⇒ Vehicle diagnostic tester in “Guided Fault Finding”

mode - air conditioning system.

♦ Constriction or obstruction in refrigerant circuit

♦ Expansion valve defective

♦ If a shut-off valve is installed in the refrigerant circuit and it does not open correctly or at all ⇒ Heating, air

conditioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-specific workshop manual).

– If fitted, check the function of the installed shut-off valve ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrig‐

erant circuit (vehicle-specific workshop manual).

– Touch the refrigerant circuit by hand to feel for a drop in temperature ⇒ Heating, air conditioning; Rep. gr.

87 ; Refrigerant circuit (vehicle-specific workshop manual). If a drop in temperature is felt on a component,

if there is a kink or bottle-neck in the hose or pipeline, renew this component. In the event of a blockage or

if no fault can be found, clean the refrigerant circuit (flush with R1234yf refrigerant)

⇒ “1.6 Cleaning refrigerant circuit”, page 92

– Renew the expansion valve and desiccant bag/desiccant cartridge (or reservoir/receiver) ⇒ page 79 and

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-specific workshop manual).

Final measures

lk

– Recharge the refrigerant circuit ⇒ “2.6 Charging refrigerant circuit”, page 146

– Repeat the test

⇒ “2.14.4 Checking pressures with air conditioning system switched on - vehicles with mechanical air

conditioning compressor”, page 183

Note

♦ In this case, the evaporator may ice up even though the correct

volume of refrigerant is present in the refrigerant circuit.

♦ If the expansion valve is defective (always closed or not open‐

ing wide enough) the air conditioner compressor regulating

valve - N280- will be set to maximum power and the low pres‐

sure value will fall to the diagram value or less (the air condi‐

tioner compressor extracts refrigerant from the low pressure

side). Since no refrigerant can flow through the expansion

valve, however, the cooling output is not reached and the high

pressure may also not increase or only increase slightly owing

to there being no energy exchange ⇒ Vehicle diagnostic tester

in “Guided Fault Finding” mode - air conditioning system and

⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit

(vehicle-specific workshop manual).

♦ If there is too much refrigerant in the refrigerant circuit, the air

conditioner compressor must be emptied and the desiccant

bag (desiccant cartridge) or reservoir/receiver renewed. After

cleaning (flushing with R1234yf refrigerant)

⇒ “1.6 Cleaning refrigerant circuit”, page 92 the refrigerant cir‐

cuit, pour the correct volume of refrigerant oil in the refrigerant

circuit ⇒ Heating, air conditioning; Rep. gr. 00 ; Technical

data; Approved refrigerant oils and refrigerant oil fill volumes

(vehicle-specific workshop manual) and ⇒ Heating, air con‐

ditioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-specific

workshop manual).

♦ If the specification is not reached again when the test is re‐

peated but no fault can be found in the refrigerant circuit, clean

the refrigerant circuit (flush with R1234yf refrigerant)

⇒ “1.6 Cleaning refrigerant circuit”, page 92 .

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

Possible deviation from specification during pressure test

♦ The requisite cooling output is reached initially but after a while or after an extended period, the cooling

output is no longer sufficient.

♦ The high pressure and the low pressure are normal to start with

♦ After some time, the high pressure rises above the specification, the low pressure still equates to the

specification or it drops below the specification.

Possible causes for deviation from specification and rectification

♦ Radiator, condenser contaminated or actuation of the radiator is not OK

– Check actuation of the radiator fan and repair if necessary ⇒ Vehicle diagnostic tester in “Guided Fault

Finding” mode - air conditioning system.

– Check condenser for contamination and clean if necessary ⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerant circuit (vehicle-specific workshop manual) and ⇒ Engine, mechanicals; Rep. gr. 19 ; Radiator/

radiator fan .

♦ Actuation of the air conditioner compressor regulating valve - N280- is defective.

– Check actuation of -N280- and the measured value of evaporator output temperature sender - G263- ,

repair if necessary ⇒ Vehicle diagnostic tester in “Guided Fault Finding” mode - air conditioning system.

♦ Too much refrigerant in the refrigerant circuit

– Extract refrigerant from the refrigerant circuit ⇒ “2.4 Emptying refrigerant circuit”, page 137 .

– If the extracted refrigerant volume is considerably greater (more than 100 g) than the prescribed fill volume

⇒ Heating, air conditioning; Rep. gr. 00 ; Technical data (vehicle-specific workshop manual), there was

too much refrigerant in the refrigerant circuit Refill the refrigerant circuit with the correct volume of R1234yf

and repeat the test.

♦ Air conditioner compressor regulating valve - N280- or air conditioner compressor defective

– Check function of -N280- ; if necessary remove -N280- and check for dirt ⇒ Vehicle diagnostic tester in

“Guided Fault Finding” mode - air conditioning system and ⇒ “1.5 Renewing components”, page 79

– -N280- or renew the air conditioner compressor ⇒ “1.5 Renewing components”, page 79

– If dirt is found in the refrigerant circuit, clean the refrigerant circuit (flush with R1234yf refrigerant) and renew

the expansion valve and desiccant bag/desiccant cartridge (or renew the receiver/reservoir)

⇒ “1.5 Renewing components”, page 79 and ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit

lk

(vehicle-specific workshop manual) and ⇒ “1.6 Cleaning refrigerant circuit”, page 92 .

♦ Too much refrigerant oil in the refrigerant circuit

♦ Moisture in refrigerant circuit

– Extract refrigerant from the refrigerant circuit ⇒ “2.4 Emptying refrigerant circuit”, page 137 .

– If the extracted refrigerant volume equates to the prescribed fill volume or is marginally lower (max. 100 g)

⇒ Heating, air conditioning; Rep. gr. 00 ; Technical data (vehicle-specific workshop manual), there is too

much refrigerant oil in the refrigerant circuit

– Clean refrigerant circuit (flush with R1234yf refrigerant) ⇒ “1.6 Cleaning refrigerant circuit”, page 92 .

– Renew the expansion valve and desiccant bag/desiccant cartridge (or reservoir/receiver)

⇒ “1.5 Renewing components”, page 79 and ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit

(vehicle-specific workshop manual).

Final measures

– Recharge the refrigerant circuit ⇒ “2.6 Charging refrigerant circuit”, page 146

– Repeat the test

⇒ “2.14.4 Checking pressures with air conditioning system switched on - vehicles with mechanical air

conditioning compressor”, page 183

2. Working with air conditioner service station

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

Note

♦ If there is too much refrigerant in the refrigerant circuit, the air

conditioner compressor must be emptied and the desiccant

bag (desiccant cartridge) or reservoir/receiver renewed. After

cleaning (flushing with R1234yf refrigerant)

⇒ “1.6 Cleaning refrigerant circuit”, page 92 the refrigerant cir‐

cuit, pour the correct volume of refrigerant oil in the refrigerant

circuit ⇒ Heating, air conditioning; Rep. gr. 00 ; Technical

data; Approved refrigerant oils and refrigerant oil fill volumes

(vehicle-specific workshop manual) and ⇒ Heating, air con‐

ditioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-specific

workshop manual).

♦ In this case, the evaporator may ice up even though the correct

volume of refrigerant is present in the refrigerant circuit.

♦ A fault in the evaporator output temperature sender - G263-

could also cause the refrigerant circuit to ice up. With this

complaint, also observe the measured value of -G263- ⇒ Ve‐

hicle diagnostic tester in “Guided Fault Finding” mode - air

conditioning system and ⇒ Heating, air conditioning; Rep. gr.

87 ; Overview of fitting locations - air conditioning system (ve‐

hicle-specific workshop manual).

lk

Possible deviation from specification during pressure test

♦ The requisite cooling output is reached initially but after a short or extended period, the required level is no

longer reached.

♦ The high pressure and low pressure are normal to start with but after a while, the high pressure rises above

the specification and the low pressure drops to the specification or lower.

♦ The high pressure and low pressure are normal to start with. After a while, the low pressure drops to the

specification or lower and the evaporator ices up.

Possible causes for deviation from specification and rectification

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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017

Possible deviation from specification during pressure test

♦ Radiator, condenser contaminated or actuation of the radiator is not OK

– Check actuation of the radiator fan and repair if necessary ⇒ Vehicle diagnostic tester in “Guided Fault

Finding” mode - air conditioning system.

– Check condenser for contamination and clean if necessary ⇒ Heating, air conditioning; Rep. gr. 87 ;

lk

Refrigerant circuit (vehicle-specific workshop manual) and ⇒ Engine, mechanicals; Rep. gr. 19 ; Radiator/

radiator fan .

♦ Measured value of evaporator output temperature sender - G263- faulty.

– Check measured value and installation of -G263- ⇒ Vehicle diagnostic tester in “Guided Fault Finding”

function - air conditioning system and ⇒ Heating, air conditioning; Rep. gr. 87 ; Overview of fitting locations

- air conditioning system .