Get Air conditioning system -> 2.14.4 Checking pressures with air conditioning system switched on - vehicles with mechanical air conditioning compressor 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

⇒ “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 .

2. Working with air conditioner service station

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

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

180

Rep. gr.87 - Air conditioning system

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

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).

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♦ 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.

2. Working with air conditioner service station

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

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

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⇒ “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 .

182

Rep. gr.87 - Air conditioning system

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

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).

2. Working with air conditioner service station

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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.

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– 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.

184

Rep. gr.87 - Air conditioning system

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

– 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

Rep. gr.87 - Air conditioning system

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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).

lk

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

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

190

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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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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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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 .

196

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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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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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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 .