Get Refrigerant circuit -> Working with the air conditioner service station Guide for Audi A2 SUV 1999-2005

Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A1 Sportback 2 ...

Air conditioner with refrigerant R134a - Edition 11.2018

5.3

Working with the air conditioner service

station

Vehicles with high-voltage system (hybrid vehicles)

High voltage! Danger to life!

The voltage levels in the high-voltage system constitute a safety

hazard. Danger of severe or fatal injuries from electric shock.

– Persons with life-sustaining or other electronic medical devi‐

ces in or on their body must not perform any work on the high-

voltage system. Such medical devices include internal anal‐

gesic pumps, implanted defibrillators, pacemakers, insulin

pumps and hearing aids.

– The high-voltage system must be de-energised by a suitably

qualified person.

Risk of injury - engine may start unexpectedly

It is difficult to determine whether the drive system of an electric

vehicle or hybrid vehicle is active. Moving parts can trap or draw

in parts of the body.

– Switch off ignition.

– Place ignition key outside vehicle.

Risk of damage to high-voltage wiring

Incorrect handling may result in damage to the insulation of high-

voltage wires or high-voltage connectors.

– Never use high-voltage wiring or high-voltage connectors as

a support.

– Never prop tools against high-voltage wiring or high-voltage

connectors.

– Never bend or kink high-voltage wiring.

– Pay attention to coding when connecting high-voltage con‐

nections.

♦ For all work on vehicles with high-voltage system, note addi‐

tional warnings for working on such vehicles

⇒ “1 Warning instructions when working on vehicles with high-

voltage system”, page 1 .

♦ If work near high-voltage system components is necessary,

perform a visual check of the high-voltage components and

wires to check for damage ⇒ page 2 .

♦ If work on high-voltage system components is necessary, de-

energise high-voltage system ⇒ Rep. gr. 93 ; De-energising

high-voltage system or ⇒ Electrical system; Rep. gr. 93 ; De-

energising high-voltage system .

– To minimise the number of automatic engine starts when the

vehicle's drive system is active during test and measurement

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

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

system; General information; Rep. gr. 27 ; Battery; Charging

5. Refrigerant circuit

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Air conditioner with refrigerant R134a - Edition 11.2018

battery and ⇒ Electrical system; Rep. gr. 93 ; General warning

instructions 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 take care to keep well clear of the engine

when it is running. Set up any tools needed so that they cannot

come into contact with moving parts.

Note

♦ Move the selector lever to position “P” and activate the parking

brake before performing test and measurement work for which

the ignition must be switched on but where the vehicle's drive

system does not need to be active.

♦ The status of the drive system (READY) is shown by the con‐

trol unit in dash panel insert - J285- via the “power meter” ⇒

Owner's Manual .

♦ Activating and deactivating drive system ⇒ Owner's Manual

(note display of control unit in dash panel insert - J285- ).

Vehicles with start/stop system

Risk of injury - engine may start unexpectedly

The engine can start unexpectedly if the vehicle's start/stop sys‐

tem is activated. A message in the instrument cluster indicates

whether the start/stop system is activated.

– To deactivate the start/stop system, switch off the ignition.

All vehicles

Caution

♦ If there is a possibility that chemical substances (sealing

additives) for sealing leaks have been added to the refrig‐

erant circuit from which the refrigerant is to be extracted,

do not connect the air conditioner service station to this

refrigerant circuit and do not extract the refrigerant.

♦ Chemical substances (sealing additives) for sealing leaks

form deposits in the refrigerant circuit which will impair

operation of the air conditioning system and lead to failure

of the system (and of the air conditioner service station).

♦ Customers should be informed that the air conditioner in

their vehicle contains substances not approved by Audi

and that the system can therefore not be discharged and

serviced by your workshop.

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Rep. gr.87 - Air conditioning system

Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A1 Sportback 2 ...

Air conditioner with refrigerant R134a - Edition 11.2018

Note

♦ Commercially available chemical substances (sealing addi‐

tives) for sealing refrigerant circuit leaks are not approved by

Audi AG. Damage to or malfunctioning of the air conditioner

or air conditioner service station cannot be precluded as no

tests have been performed to establish long-term action, ef‐

fectiveness and material compatibility.

♦ Commercially available sealing additives have different phys‐

ical and chemical properties. They may have a lasting detri‐

mental effect on operation of the air conditioner and air

conditioner service station or even be the cause of total failure.

♦ Audi objects to the use of chemical substances (sealing addi‐

tives) for sealing leaks in refrigerant circuits.

♦ Chemical substances (sealing additives) for sealing leaks in

the refrigerant circuit generally react with the ambient air or the

humidity contained in it. They cause malfunctioning of valves

and other components with which they come into contact on

account of deposits in the refrigerant circuit (and in the air

conditioner service station being used). These deposits can

no longer be completely removed from the components (not

even by cleaning/flushing with refrigerant R134a).

♦ Chemical substances (sealing additives) used to seal leaks in

refrigerant circuits usually cannot be detected from the out‐

side; mostly the stickers that are supposed to be attached to

identify these chemical substances are missing. Therefore, act

with caution when working on a vehicle whose past you are

not familiar with.

♦ On the accessories market, vessels with integrated filters are

available which are supposed to intercept these chemical sub‐

stances (additives used to seal leaks). As Audi are not aware

of the composition and thus the physical and chemical prop‐

erties of these substances, no information can be given here

as to the effectiveness and the separation rate of such filters.

♦ The sealant filter - VAS 6592- available as "Workshop equip‐

ment" provides a certain degree of protection for air condition‐

er service stations. This filter is incorporated between the air

conditioner service station and the service connection on the

low-pressure side of the vehicle refrigerant circuit (the air con‐

ditioner service station is not to be attached to the service

connection on the high-pressure side of the refrigerant circuit

for drainage, evacuation and measurement). The filter sepa‐

rates out certain substances added to the circuit to seal re‐

frigerant circuit leaks. It thus prevents the unimpeded and

unrestricted ingress of these substances into the air condi‐

tioner service station (together with the refrigerant and refrig‐

erant oil) where they would cause damage. Protection is

however only provided if the built-in filter is replaced at regular

intervals exactly as specified by the manufacturer in the ap‐

plicable instructions. As Audi do not approve the use of chem‐

ical substances (sealing additives) for sealing leaks in the

refrigerant circuit and the composition of such chemical sub‐

stances (sealing additives) marketed for example as so-called

“refrigerant circuit sealants” varies greatly, it is again not pos‐

sible to provide any information on the action and efficiency of

the sealant filter - VAS 6592- .

If air conditioner refrigerant circuit repair work has to be performed

on a vehicle on which chemical substances (sealing additives)

have been added to the refrigerant circuit to seal leaking compo‐

nents (or if you have good reason to believe that such substances

have been added), the customer (vehicle owner) must be notified

of the following:

5. Refrigerant circuit

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Air conditioner with refrigerant R134a - Edition 11.2018

♦ The air conditioner refrigerant cannot be extracted on account

of the substances added (sealing additives), as these could

damage the air conditioner service station. The refrigerant

must be extracted for example by a company authorised to

extract and then dispose of the contaminated refrigerant using

the appropriate equipment (e.g. a local refuse disposal com‐

pany specialising in the disposal of refrigerants).

♦ The air conditioning system can only be properly repaired by

renewing all the refrigerant circuit components which have

come into contact with the sealing additive. The sealing addi‐

tive may already have damaged certain refrigerant circuit com‐

ponents (e.g. the air conditioner compressor regulating valve

- N280- ) or lead to damage and subsequent failure shortly

after renewed start-up. Furthermore, sealing additive deposits

may subsequently come loose in the refrigerant circuit com‐

ponents and then cause the air conditioner to fail again (full

cleaning of these components with workshop equipment is

currently not possible).

Work on the air conditioner refrigerant circuit

⇒ “5.3.1 Important notes for working with the air conditioner serv‐

ice station”, page 82

⇒ “5.3.2 Connecting air conditioner service station for measuring

and testing”, page 83

⇒ “5.3.3 Discharging refrigerant circuit with air conditioner service

station”, page 84

⇒ “5.3.4 Evacuating refrigerant circuit with air conditioner service

station”, page 86

⇒ “5.3.5 Charging refrigerant circuit with air conditioner service

station”, page 91

⇒ “5.3.6 Starting up air conditioner after charging”, page 92

⇒ “5.3.7 Pouring refrigerant into reservoir (charging cylinder or

storage vessel) of air conditioner service station”, page 94

⇒ “5.3.8 Discharging air conditioner service station”, page 94

5.3.1

Important notes for working with the air

conditioner service station

Observe the following in order to operate the air conditioner serv‐

ice stations, currently available air conditioner service stations ⇒

Electronic parts catalogue (Tools; Workshop equipment/tools; Air

conditioning/heating):

– The fitted filter and dryer must be renewed by no later than

when the operational time specified in the related operating

instructions has been reached.

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

the refrigerant circuit, the dryers and filters fitted must be re‐

newed more frequently ⇒ page 95 .

– Use only refrigerant oils which are also approved for the ve‐

hicle-specific refrigerant circuit (if applicable, add the refriger‐

ant oil directly to the refrigerant circuit). ⇒ Electronic parts

catalogue

In cases of doubt about the composition of the refrigerant extrac‐

ted from the refrigerant circuit, this is not to be re-used even after

cleaning in the air conditioner service station.

– In such cases, discharge the air conditioner service station

⇒ page 187 , clean the system if necessary and renew the

filters, dryers and refrigerant oil.

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Rep. gr.87 - Air conditioning system

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Air conditioner with refrigerant R134a - Edition 11.2018

– In Germany, for example, contaminated refrigerant can be re‐

turned to the refrigerant supplier in so-called recycling cylin‐

ders for treatment or environmentally friendly disposal (differ‐

ent or additional regulations may apply in individual countries).

Commercially available air conditioner service stations can be

classified in 2 groups:

♦ Air conditioner service stations which clean the refrigerant ex‐

tracted from a vehicle for re-use (so-called extraction and

recycling stations, for currently available air conditioner serv‐

ice stations) ⇒ Electronic parts catalogue (Tools; Workshop

equipment/tools; Air conditioning/heating).

♦ Air conditioner service stations which transfer extracted re‐

frigerant to recycling cylinders (for large-scale recycling);

these are referred to as extraction systems.

5.3.2

Connecting air conditioner service sta‐

tion for measuring and testing

•

Work procedure may vary depending on the type of tools se‐

lected; therefore it is important to observe the tool-specific

operating instructions.

Note

The work procedure must always be performed as described in

the operating instructions of the air conditioner service station.

The filler hoses should be connected as follows to prevent air or

moisture from entering into the refrigerant circuit:

– On vehicles with high-voltage system, switch off (deactivate)

auxiliary air conditioner function ⇒ Owner's Manual and ⇒

Infotainment/MMI Operating Manual .

– Switch off ignition.

– Connect air conditioner service station to power supply.

– Unscrew sealing caps from service connections / connections

with valve ⇒ Heating, air conditioning; Rep. gr. 87 ; Refriger‐

ant circuit (vehicle-specific Workshop Manual).

– Evacuate filler hoses if necessary.

– Connect quick-release coupling to service connection of re‐

frigerant circuit.

WARNING

♦ Do not open the valves on the low or high-pressure end

with the engine running, as otherwise the air conditioner

compressor or the air conditioner service station could be

destroyed by a short circuit between the high and low-

pressure ends of the refrigerant circuit if the air condition‐

ing system is switched on.

– Only screw the handwheel into the quick-release coupling

adapter to the extent required to reliably open the valve in the

service connection (observe the pressure gauge; take care not

to open the valve too far).

– Start the engine and perform the intended tests and meas‐

urements.

5. Refrigerant circuit

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– Compare the values determined to the specified measured

values ⇒ page 193 .

– Before detaching quick-release coupling, close it by screwing

out handwheel.

Vehicles with one service connection only:

Note

Screw valve adapters - V.A.G 1785/9- , -V.A.G 1785/10- or adapt‐

er set - V.A.G 1786- onto refrigerant circuit connections with valve

and bleed filler hoses while connecting to adapters (faintly audible

escape of refrigerant gas is permitted) ⇒ page 187 .

– The filler hose must be fitted with a valve opener for opening

valve in valve adapter.

On vehicles with high-voltage system and additional air condi‐

tioner functions (e.g. on the Audi Q7 e-tron):

Note

On vehicles with the “heat pump” and/or “high-voltage battery

cooling” function, high pressure is not available at the service

connection on the high-pressure side in all air conditioner oper‐

ating modes. On these vehicles, the pressure in the refrigerant

circuit on the high-pressure side can only be measured via the

pressure/temperature senders installed in the refrigerant circuit

(depending on the air conditioner operating mode) ⇒ Heating, air

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

Workshop Manual) and ⇒ Vehicle diagnostic tester (“Guided Fault

Finding”).

To check the various functions of these air conditioners:

– On the vehicle diagnostic tester, select the corresponding

function (“passenger compartment cooling”, “heat pump op‐

eration” or “high-voltage battery cooling”) and perform the

function according to requirements ⇒ Vehicle diagnostic tester

in “Guided Fault Finding” mode.

– On the vehicle diagnostic tester, select and read out the meas‐

urements from the various pressure/temperature senders in‐

stalled in the refrigerant circuit ⇒ Vehicle diagnostic tester in

“Guided Fault Finding” mode.

5.3.3

Discharging refrigerant circuit with air

conditioner service station

•

Work procedure may vary depending on the type of tools se‐

lected; it is therefore important to observe the tool-specific

operating instructions.

The refrigerant circuit must be discharged if you intend to re‐

move parts of the refrigerant circuit, if there is any doubt about

the quantity of refrigerant in the circuit or if safety precautions

require you to do so.

•

All the necessary usage information for working with the re‐

frigerant air conditioner service station can be found in the air

conditioner service station operating instructions.

Discharging:

– On vehicles with high-voltage system, switch off (deactivate)

auxiliary air conditioner function ⇒ Owner's Manual and ⇒

Infotainment/MMI Operating Manual .

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Air conditioner with refrigerant R134a - Edition 11.2018

– Switch off ignition.

– Connect air conditioner service station to vehicle service con‐

nections according to operating instructions (refer to vehicle-

specific refrigerant circuit) and start up service station ⇒

Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit (ve‐

hicle-specific Workshop Manual).

Additionally on vehicles with electrically operated valves in the

refrigerant circuit which are not open when the system is de-ener‐

gised (e.g. on the Audi Q7 e-tron):

Note

On vehicles with high-voltage system and additional air condi‐

tioner functions (“heat pump operation” or “high-voltage battery

cooling”), valves which are not open when the system is de-ener‐

gised may be fitted in the refrigerant circuit. These valves are

opened and closed e.g. via stepper motors and are not activated

after the ignition is switched off. However, for the refrigerant circuit

to be discharged fully, evacuated correctly and filled there must

be no separated areas; these valves must therefore be opened

before performing such work ⇒ Heating, air conditioning; Rep.

gr. 87 ; Refrigerant circuit (vehicle-specific Workshop Manual),

and ⇒ Vehicle diagnostic tester (“Guided Fault Finding”).

– Use the vehicle diagnostic tester to open the electrically acti‐

vated valves which are not open when the system is de-

energised ⇒ Vehicle diagnostic tester (“Guided Fault Find‐

ing”).

All vehicles:

– Drain the refrigerant circuit with the air conditioner service sta‐

tion in line with the corresponding operating instructions.

Caution

Risk of air conditioner compressor damage if the refrigerant

circuit is empty

Never start the engine when the refrigerant circuit is empty.

♦ Depending on the version of the air conditioner service

station, the pressure in the refrigerant circuit may be less

than 1 bar absolute following drainage.

♦ Depending on the version, the air conditioner compressor

may be damaged by running it when the pressure in the

refrigerant circuit is low.

♦ Never start the engine if the pressure in the refrigerant

circuit is below ambient pressure.

WARNING

Risk of injury (frostbite).

Refrigerant may escape if the refrigerant circuit has not been

discharged.

Extract refrigerant before opening refrigerant circuit. Renewed

evaporation may create pressure in refrigerant circuit if refrig‐

erant circuit is not opened within 10 minutes following extrac‐

tion. Extract refrigerant again.

5. Refrigerant circuit

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Air conditioner with refrigerant R134a - Edition 11.2018

Note

♦ It is impossible to exclude the possibility that refrigerant oil may

be extracted from the refrigerant circuit along with the refrig‐

erant. To ensure air conditioner compressor lubrication, the

refrigerant oil in the circuit must be topped up with fresh oil

⇒ page 292 .

♦ On vehicles fitted with an air conditioner compressor without

magnetic clutch (with air conditioner compressor regulating

valve - N280- ), the engine should not be run for longer than

absolutely necessary with the refrigerant circuit empty; avoid

high engine speeds (with air conditioner compressor always

in operation).

♦ On vehicles with an air conditioner compressor without a mag‐

netic clutch, the engine should only be started following the

complete assembly of the refrigerant circuit (avoid high engine

speeds).

♦ Depending on the version of the air conditioner compressor,

there may be a valve on the high-pressure side of the com‐

pressor which prevents liquid refrigerant from flowing back into

the compressor after the air conditioner has been switched off.

If an air conditioner compressor with such a valve is installed

in a vehicle with a refrigerant circuit with an expansion valve,

it may take a relatively long time before the pressure in the

high-pressure side drops (the expansion valve is cold and the

pressure in the low-pressure side increases rapidly after the

compressor is switched off; the expansion valve is closed and

the refrigerant can only flow slowly to the low-pressure side).

If the air conditioner compressor is switched on (or the refrig‐

erant circuit is discharged via the low-pressure side), the

pressure on the low-pressure side drops, the expansion valve

is opened and the refrigerant can flow to the low-pressure side.

♦ The quantity of refrigerant R134a extracted as displayed by

the air conditioner service station may differ from the amount

actually extracted depending on the version of the air condi‐

tioner service station, the mode in which the air conditioner

service station was last operated and the ambient temperature

etc. The quantity of refrigerant extracted as displayed by the

air conditioner service station is therefore only a guide to the

amount of refrigerant actually extracted from the refrigerant

circuit. Attention should also be paid to the operating instruc‐

tions and technical product description of the air conditioner

service station.

If, after drainage, work not requiring the air conditioner service

station is to be performed on the vehicle,

– disconnect the air conditioner service station from the refrig‐

erant circuit and switch it off.

If evacuating and re-charging refrigerant circuit after it is dis‐

charged, refer to ⇒ page 91 .

5.3.4

Evacuating refrigerant circuit with air

conditioner service station

•

The work procedure must always be performed as described

in the operating instructions of the air conditioner service sta‐

tion.

•

Quantity of refrigerant oil in refrigerant circuit checked and if

necessary corrected ⇒ page 292 .

Quantity of refrigerant in air conditioner service station

checked

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Rep. gr.87 - Air conditioning system

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Air conditioner with refrigerant R134a - Edition 11.2018

The refrigerant circuit must be evacuated (emptied of air) before

it is charged with refrigerant. Moisture is also extracted from the

circuit.

Leaks can be detected on evacuating the refrigerant circuit.

Evacuating:

Caution

♦ Do not start the engine during the evacuating procedure

and while there is a vacuum in the refrigerant circuit.

♦ The air conditioner compressor may be damaged if the

engine is started whilst there is a vacuum in the refrigerant

circuit.

♦ Always charge the refrigerant circuit before starting the

engine.

– On vehicles with high-voltage system, switch off (deactivate)

auxiliary air conditioner function ⇒ Owner's Manual and ⇒

Infotainment/MMI Operating Manual .

– Switch off ignition.

– Connect air conditioner service station to power supply.

– Connect filler hoses of air conditioner service station to vehicle

refrigerant circuit with quick-release coupling adapter (refer to

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

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

Manual).

– Screw in the handwheel of the quick-release coupling adapt‐

ers to the extent required to reliably open the valves of the

service connections (take care not to open the valve too far).

Note

If you intend to measured the pressure on only one side of the

refrigerant circuit after charging the system (on vehicles with a

service connection), use the valve adapter and filler hose with

valve opener ⇒ page 187 .

Additionally on vehicles with electrically operated valves in the

refrigerant circuit which are not open when the system is de-ener‐

gised (e.g. on the Audi Q7 e-tron):

5. Refrigerant circuit

87

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Air conditioner with refrigerant R134a - Edition 11.2018

Note

♦ On vehicles with high-voltage system and additional air con‐

ditioner functions (“heat pump operation” or “high-voltage bat‐

tery cooling”), valves which are not open when the system is

de-energised may be fitted in the refrigerant circuit. These

valves are opened and closed e.g. via stepper motors and are

not activated after the ignition is switched off. However, for the

refrigerant circuit to be discharged fully, evacuated correctly

and filled there must be no separated areas; these valves must

therefore be opened before performing such work ⇒ Heating,

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

cific Workshop Manual), and ⇒ Vehicle diagnostic tester (“Gui‐

ded Fault Finding”).

♦ Non-return valves in the refrigerant circuit have a specific

holding pressure (approx. 0.1 bar or 100 mbar) in the forward

direction. All electrically activated valves must therefore be

open so that the refrigerant circuit can be evacuated fully (re‐

sidual pressure less than 5 mbar).

– Use the vehicle diagnostic tester to open the electrically acti‐

vated valves which are not open when the system is de-

energised ⇒ Vehicle diagnostic tester (“Guided Fault Find‐

ing”).

All vehicles:

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

frigerant circuit for at least 30 minutes. In this process, the

pressure reading must be less than 10 mbar absolute (corre‐

sponding to a vacuum of 990 mbar).

Note

On the air conditioner service station V.A.G 1885 for currently

available air conditioner service stations ⇒ Electronic parts cata‐

logue (Tools; Workshop equipment/tools; Air conditioning/heat‐

ing), the two green LEDs light at this pressure, for example.

– Switch off air conditioner service station and allow to stand for

at least 1 hour.

•

If the vacuum display (LED chain) does not change, the sys‐

tem is free of leaks and can be charged.

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Air conditioner with refrigerant R134a - Edition 11.2018

Note

♦ With V.A.G 1885 for example, for currently available air con‐

ditioner service stations ⇒ Electronic parts catalogue (Tools;

Workshop equipment/tools; Air conditioning/heating), a cur‐

rent vacuum display (LED) is only obtained after pressing the

Evacuation button again.

♦ If, with this air conditioner service station, the upper (green)

LEDs do not light immediately after switching on, either the

refrigerant circuit is leaking or there is still residual moisture/

refrigerant in the circuit.

Proceed as follows if the vacuum is not maintained or an ade‐

quate vacuum cannot be generated:

♦ The pressure in the refrigerant circuit only increases slowly

following evacuation, e.g. due to the evaporation of refrigerant

from the refrigerant oil.

– If it is not certain whether the refrigerant circuit is really leak-

proof, repeat evacuation and observe the vacuum display over

a lengthy period. Only charge circuit if vacuum is maintained.

– If it is certain that there are no leaks in the refrigerant circuit,

charging can be performed.

♦ In the event of a leak of such a magnitude that the ingress of

air on evacuation is already sufficient to prevent the air con‐

ditioner service station generating an adequate vacuum or the

vacuum gauge already indicates the ingress of air and the loss

of vacuum immediately after switching off the air conditioner

service station.

– Determine the leakage location in the refrigerant circuit as fol‐

lows:

5. Refrigerant circuit

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Note

♦ A major leak can be determined for example by building up a

pressure of max. 15 bar in the refrigerant circuit with pure, dry

compressed air or with nitrogen ⇒ page 95 . If the leak is of

large enough, the location of the leak can be found due to the

noise of the gas escaping.

♦ Apply the compressed air or the nitrogen to the closed refrig‐

erant circuit by way of the service connection to which a quick-

release coupling adapter for service connections has been

attached.

♦ The quick-release coupling adapter for service connections

can be connected to the workshop compressed air system

using e.g. a modified filler hose -A- (e.g. with a 5/8"-18 UNF

thread, depending on thread on quick-release coupling adapt‐

er) and an appropriate adapter -B- ⇒ page 383 . To prevent

moisture, oil and dirt from the workshop compressed air sys‐

tem from entering the air conditioner refrigerant circuit, also

use a combination fine filter unit for the compressed air sys‐

tem, with an oil, dirt and water separator, as commonly used

for painting systems. Install this unit between the compressed

air system and the filler hose -A- ⇒ Electronic parts catalogue

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

♦ Using a pressure gauge set with nitrogen pressure reducer

-1- (max. reducing pressure: 15 bar), a compressed-gas cyl‐

inder -3- filled with nitrogen can be connected to the service

connection (quick-release coupling adapter for service con‐

nections attached) at the closed refrigerant circuit

⇒ page 382 with a filler hose -2- (e.g. with a 5/8"-18 UNF

thread).

– Slowly increase the pressure in the refrigerant circuit to max.

15 bar.

WARNING

♦ There may be an uncontrolled flow of nitrogen out of the

cylinder.

♦ Only use pressure reducer for nitrogen cylinders (max.

working pressure 15 bar).

♦ For leak detection with nitrogen (max. permissible oper‐

ating pressure 15 bar) always work with pressure reducers

for nitrogen cylinders.

♦ Use appropriate extraction units to draw off the gas mix‐

ture escaping from the components.

– Determine the leakage location by way of the noise caused by

the escaping gas at this point.

– Eliminate the leakage.

– Evacuate and again observe the vacuum display over a period

of hours. Only charge circuit if vacuum is maintained.

♦ In the event of a leakage of a magnitude permitting the ingress

of no or very little air and the air conditioner service station can

generate an adequate vacuum. The vacuum display does not

increase or only increases very slowly after switching off the

air conditioner service station, indicating that air is only in‐

gressing and vacuum is being lost through a minor leak.

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Rep. gr.87 - Air conditioning system

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Air conditioner with refrigerant R134a - Edition 11.2018

– Pour 100 g of refrigerant into the circuit and use an electronic

leak detector to locate and eliminate any leaks ⇒ page 172 or

pour in refrigerant with UV contrast medium and use the leak

detection system VAS 6201 to search for and eliminate the

leak in the refrigerant circuit ⇒ page 173 .

– If necessary, discharge refrigerant circuit ⇒ page 84 .

– Evacuate refrigerant circuit and observe vacuum display again

over a period of hours. Only charge circuit if vacuum is main‐

tained.

5.3.5

Charging refrigerant circuit with air con‐

ditioner service station

Note

The entire refrigerant charge can be added to either the high or

low-pressure side ⇒ page 292 .

•

The work procedure must always be performed as described

in the operating instructions of the air conditioner service sta‐

tion.

•

Before pouring in refrigerant, correct the quantity of refrigerant

oil ⇒ page 292 .

When charging the refrigerant circuit, the air conditioner serv‐

ice station must be on the same level as the vehicle in which

the refrigerant circuit is to be charged (maximum difference 50

cm). Depending on the design of the air conditioner service

station , an excessive difference in height could lead to differ‐

ences between the quantity of refrigerant displayed and that

actually poured in. The charging accuracy of the air condition‐

er service station may change.

– On vehicles with high-voltage system, switch off (deactivate)

auxiliary air conditioner function ⇒ Owner's Manual and ⇒

Infotainment/MMI Operating Manual .

– Switch off ignition.

– Evacuate refrigerant circuit with air conditioner service station

⇒ page 86 .