Get Checking pressures -> Checking pressures - vehicles with electrically driven air conditioner compressor (vehicles with high-voltage system) 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

Possible deviation from speci‐

fication

Possible causes of fault

Fault elimination

•

High and low pressure nor‐ ♦ Actuation of air conditioner compres‐ – Check activation of -N280- ⇒

mal

sor regulating valve - N280- not OK

Heating, air conditioning;

Rep. gr. 87 ; Refrigerant cir‐

cuit (vehicle-specific Work‐

shop Manual).

•

Required cooling output is ♦ Too much refrigerant in circuit

attained.

♦ Expansion valve defective

– Discharge refrigerant circuit.

– Clean refrigerant circuit

(flush with refrigerant R134a

⇒ page 100 or blow out with

compressed air and nitrogen

⇒ page 95 ).

– Add correct quantity of refrig‐

erant oil to circuit (refer to

note).

•

High and low pressure nor‐

mal

Noise from air conditioner

compressor (particularly af‐

ter being switched on)

– Re-charge refrigerant circuit.

– Repeat test if operation is not

OK:

•

Required cooling output is

attained.

– Renew expansion valve.

– Re-charge refrigerant circuit.

– Repeat test.

Note

♦ Overfilling with refrigerant oil may occur if, for example, the air

conditioner compressor has been renewed without adjusting

the quantity of refrigerant oil.

♦ If the expansion valve is defective (permanently open), the

evaporator temperature is no longer regulated such that only

refrigerant in gas form exits from the evaporator. Under certain

usage conditions, liquid droplets may then be drawn in by the

air conditioner compressor and result in noise (liquid cannot

be compressed).

♦ If there is too much refrigerant oil in the circuit, discharge the

air conditioner compressor and renew the receiver. After

cleaning the refrigerant circuit (flush with refrigerant R134a

⇒ page 100 or blow out with compressed air and nitrogen

⇒ page 95 ), add the correct amount of refrigerant oil to the

circuit ⇒ page 333 .

8.6

Checking pressures - vehicles with electrically driven air conditioner com‐

pressor (vehicles with high-voltage system)

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.

230

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

– 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 .

Note

The work on the refrigerant circuit using the air conditioner service

station (here: checking pressure) described in the following can

only be carried out when the vehicle's drive system is active; if

necessary, re-energise the 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

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

8. Checking pressures

231

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

Air conditioner with refrigerant R134a - Edition 11.2018

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- ).

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

auxiliary air conditioner function ⇒ Owner's Manual and ⇒

Infotainment/MMI Operating Manual .

– Switch off ignition.

⇒ “7 Connecting air conditioner service station ”, page 187

⇒ “8 Checking pressures”, page 193

Note

If problems are only encountered at one evaporator on vehicles

fitted with two evaporators (one in air conditioning unit and one in

battery cooling module or heat exchanger for high-voltage bat‐

tery), check whether the pressures in the refrigerant circuit are

OK. Check the pipe connection between the problematic evapo‐

rator and the outgoing pipe connection at the refrigerant pipe

distribution point (for cross-sectional restriction or blockage, e.g.

in restrictor in the refrigerant line to the heat exchanger for high-

voltage battery). If no fault is found, discharge the refrigerant

circuit and re-fill it with the specified quantity of refrigerant. Then

check the pressures and the cooling output of the air conditioner

again. If the problem persists, check/renew the following compo‐

nents: if the problem only occurs on the evaporator in the air

conditioning unit, check/renew the shut-off valve upstream of the

evaporator (e.g. -N516- or -N541- ). When not activated, this

component is open and allows the refrigerant to flow through.

Renew the expansion valve at the evaporator in the air condition‐

ing unit if no fault is found on -N516- / -N541- . If the problem only

occurs on the evaporator for cooling the high-voltage components

(e.g. in the battery cooling module), check the actuation of shut-

off valve -N517- on the expansion valve on the evaporator in the

battery cooling module (when not activated, it is closed and does

not allow the refrigerant to flow through). If the problem only oc‐

curs on the heat exchanger for high-voltage battery, check the

shut-off valve -N542- (the valve is open when it is not activated

and allows refrigerant to flow through) and the restrictor integrated

in the refrigerant line ⇒ Heating, air conditioning; Rep. gr. 87 ;

Refrigerant circuit (vehicle-specific Workshop Manual).

– Check the pressures in the refrigerant circuit (with the air con‐

ditioner service station) with the ignition switched off

⇒ page 195 .

The pressures with the ignition switched off correspond to the

specifications.

– 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

232

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

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

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

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

instructions for work on the high-voltage system .

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.

♦ On vehicles with a high-voltage system, the engine does not

have to be running to check the pressures in the refrigerant

circuit.

♦ 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 vehicle drive system (check "READY" display in

control unit in dash panel insert - J285- ) ⇒ Owner's Manual

– Activate vehicle drive system ⇒ Owner's Manual .

– Switch on air conditioner.

– Observe the pressure reading (e.g. pressure gauge) of the air

conditioner service station.

Note

♦ The electrically driven air conditioner compressor is actuated

by the vehicle electronics. The engine speed has no influence

on the cooling output of the air conditioner.

♦ When the vehicle is stationary or only moving slowly (up to a

speed of approx. 45 km/h), the air conditioner compressor is

not activated at the maximum specified speed (of approx.

8500 rpm); the air conditioner compressor speed is limited to

approx. 5000 rpm.

♦ Activation of the electrically driven air conditioner compressor

can be monitored via Guided Fault Finding ⇒ Vehicle diag‐

nostic tester, “Guided Fault Finding” mode for air conditioner

and battery regulation .

♦ Measure the pressures at the service connections; the fitting

locations of these connections are vehicle-specific ⇒ Heating,

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

cific Workshop Manual).

8. Checking pressures

233

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

Air conditioner with refrigerant R134a - Edition 11.2018

⇒ “8.6.1 Specifications for pressures in refrigerant circuit on ve‐

hicles without heat pump”, page 234

⇒ “8.6.2 Specifications for pressures in refrigerant circuit on ve‐

hicles with heat pump”, page 254

8.6.1

Specifications for pressures in refriger‐

ant circuit on vehicles without heat pump

Note

No non-return valves are installed in the refrigerant circuit on ve‐

hicles with high-voltage system on which no heat pump is fitted

(e.g. Audi A3 e-tron, Audi Q5 hybrid, Audi A6 hybrid and Audi A8

hybrid). On these vehicles, however, valves are installed in the

refrigerant circuit with regulate the flow of refrigerant to the evap‐

orator (in the heater and air conditioning unit) or to the heat

exchanger for cooling high-voltage system components. These

valves only have 2 operating positions (open or closed) ⇒ Heat‐

ing, air conditioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-

specific Workshop Manual) and ⇒ Vehicle diagnostic tester in

“Guided Fault Finding” mode for air conditioner and battery reg‐

ulation .

High-pressure side:

Increasing from initial pressure (when connecting pressure

gauges) up to max. 20 bar

Low-pressure side:

Dropping from initial pressure (when connecting pressure

gauges) to a value between 1.5 and 2.3 bar absolute (depending

on cooling output required)

Air conditioner compressor speed:

Between 800 and 8600 rpm depending on cooling output required

(currently max. 5000 rpm with vehicle stationary)

234

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

♦ The temperature of the air downstream of the evaporator, the

current air conditioner compressor speed and the refrigerant

pressure on the high-pressure side are displayed as meas‐

ured values by various control units depending on the vehicle

(e.g. operating and display unit, Climatronic control unit -

J255- , operating and display unit for front air conditioning

system - E87- , thermal management control unit - J1024- etc.)

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

air conditioner and ⇒ Current flow diagrams, Electrical fault

finding and Fitting locations.

♦ If a very high cooling output is required (e.g. high ambient

temperature and high fresh air blower speed), the air condi‐

tioner compressor cannot initially set the pressure on the low-

pressure side to the necessary value (e.g. for a certain time

after switching on the air conditioner). When the vehicle is sta‐

tionary or only moving slowly (up to a speed of approx. 45 km/

h), the air conditioner compressor is not activated at the max‐

imum specified speed (of approx. 8500 rpm); the air condi‐

tioner compressor speed is limited to approx. 5000 rpm.

Limitation of the maximum permissible air conditioner com‐

pressor speed is only cancelled at vehicle speeds above

approx. 45 km/h. At an air conditioner compressor speed of

5000 rpm, with a high ambient temperature and a high fresh

air blower speed (unfavourable ambient conditions), the out‐

put (delivery volume) of the air conditioner compressor is not

initially sufficient to reduce the pressure on the low-pressure

side to the specified value. One way of checking the control

action of the air conditioner compressor under these condi‐

tions is to actuate 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 using the

“Guided Fault Finding” function of the air conditioner and the

battery regulation and ⇒ Heating, air conditioning; Rep. gr.

00 ; Repair instructions; Checking the cooling output (vehicle-

specific Workshop Manual).

♦ Under unfavourable conditions (very high ambient tempera‐

tures, high humidity), the pressure on the high-pressure side

may increase to max. 29 bar.

♦ The specified speed of the air conditioner compressor is dis‐

played as a measured value by various control units depend‐

ing on the vehicle (e.g. operating and display unit, Climatronic

control unit - J255- ) ⇒ Vehicle diagnostic tester in “Guided

Fault Finding” mode for air conditioning system and ⇒ Current

flow diagrams, Electrical fault finding and Fitting locations).

♦ The high pressure measured by the corresponding sender

(e.g. refrigerant pressure and temperature sender - G395- or

pressure sender for refrigerant circuit - G805- ) is displayed as

a measured value by the corresponding control unit (e.g. op‐

erating and display unit, Climatronic control unit - J255- ) ⇒

Vehicle diagnostic tester in “Guided Fault Finding” mode for

air conditioner and ⇒ Heating, air conditioning; Rep. gr. 00 ;

Repair instructions; Checking cooling output (vehicle-specific

Workshop Manual).

♦ Depending on the speed of the air conditioner compressor and

the control characteristic of the expansion valve, the low pres‐

sure settles in the tolerance band within the air conditioner

compressor output range (1.5 to 2.3 bar).

♦ The specified air conditioner compressor speed must be high‐

er than 1500 rpm for this test.

8. Checking pressures

235

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

Air conditioner with refrigerant R134a - Edition 11.2018

♦ In the “maximum cooling output” setting, the specified speed

is regulated to approx. 4000 to 5000 rpm. This value is vehicle-

specific and is displayed as a measured value by the corre‐

sponding control unit (e.g. operating and display unit,

Climatronic control unit - J255- ) ⇒ Vehicle diagnostic tester

in “Guided Fault Finding” mode for air conditioner and battery

regulation .

♦ On the absolute pressure scale, 0 bar corresponds to an ab‐

solute vacuum. Normal ambient pressure corresponds to an

absolute pressure of 1 bar. On the scale of most pressure

gauges, 0 bar corresponds to an absolute pressure of 1 bar

(can be seen from -1 bar mark below 0) ⇒ Vehicle diagnostic

tester using the “Guided Fault Finding” function for the air con‐

ditioner and ⇒ Heating, air conditioning; Rep. gr. 00 ; Repair

instructions; Checking the cooling output (vehicle-specific

Workshop Manual).

♦ On vehicles with two evaporators (e.g. Audi A8 hybrid: one in

the air conditioning unit and one for cooling the high-voltage

components e.g. in the battery cooling module / Audi A3 e-

tron: in the heat exchanger for high-voltage battery), if the

measured temperature corresponds to or is below the speci‐

fied value at one evaporator but the required specified value

is not attained at the other evaporator, the system is controlled

as follows: the responsible control unit ( -J840- or -J255- ) ac‐

tivates the electric air conditioner compressor - JX1- at a

higher speed via various other control units (e.g. power and

control electronics for electric drive - J842- and control unit for

air conditioning compressor - V470- ). This causes the cooling

output of the air conditioner to increase and the pressure on

the low-pressure side and the evaporator temperature to drop.

If the required temperature value is then not reached at one

evaporator, the relevant control unit (e.g. the -J840- or -J255- )

actuates the integrated shut-off valves ( -N516- , -N541- , -

N517- or -N542- ) so that refrigerant no longer flows through

the evaporator which is too cold ⇒ Vehicle diagnostic tester

in “Guided Fault Finding” mode for air conditioner , ⇒ Current

flow diagrams, Electrical fault finding and Fitting locations and

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

Checking the cooling output (vehicle-specific Workshop Man‐

ual).

♦ As the output of the evaporator for cooling the high-voltage

components (in the battery cooling module and in the high-

voltage battery heat exchanger) is considerably less than that

of the evaporator in the air conditioning unit, the required tem‐

perature may still be reached in the evaporator for cooling the

high-voltage components when there is insufficient refrigerant

in the circuit, but the required temperature will no longer be

reached at the evaporator in the air conditioning unit (although

the air conditioner compressor is being activated at a higher

speed).

236

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

Possible deviation from speci‐

fication

Possible causes of fault

Fault elimination

•

High pressure remains con‐ ♦ Actuation of air conditioner compres‐ – Check actuation and opera‐

stant or only increases

slightly (above pressure

with engine stopped)

sor not OK ⇒ Vehicle diagnostic tester,

“Guided Fault Finding” function for air

conditioner, air conditioner compres‐

sor and battery regulation .

tion of the air conditioner

compressor

– Extract refrigerant from re‐

frigerant circuit.

•

Low pressure drops quickly

to specified value or below. ♦ Not enough refrigerant in circuit

Required cooling output is ♦ Expansion valve for evaporator in air

•

If quantity of refrigerant ex‐

tracted is substantially less

than specified capacity:

not attained in evaporator in

air conditioning unit and in

evaporator for cooling high-

voltage components.

conditioning unit defective.

♦ Shut-off valve upstream of evaporator

in air conditioning unit (e.g. -N516- or -

N541- , depending on vehicle) faulty

(blocked) ⇒ Heating, air conditioning;

Rep. gr. 87 ; Refrigerant circuit (vehi‐

cle-specific Workshop Manual).

– Locate leak with leak detec‐

tor and repair it.

– Re-charge refrigerant circuit.

– Repeat test.

•

If amount of refrigerant ex‐

tracted roughly corresponds

to specified capacity:

•

High pressure normal

Low pressure corresponds

to specified value

– Shut-off valve upstream of

evaporator in air conditioning

unit (e.g. -N516- or -N541- ,

depending on vehicle) faulty

(blocked) ⇒ Heating, air con‐

ditioning; Rep. gr. 87 ; Re‐

frigerant circuit (vehicle-spe‐

cific Workshop Manual).

•

Required cooling output is

not attained.

– Renew expansion valve.

– Re-charge refrigerant circuit.

– Repeat test.

Note

Observe notes ⇒ page 239 .

8. Checking pressures

237

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

Air conditioner with refrigerant R134a - Edition 11.2018

Possible deviation from speci‐

Possible causes of fault

Fault elimination

fication

On vehicles without shut-off

valve upstream of evaporator

in air conditioning unit (e.g. -

N516- or -N541- , depending

on vehicle) ⇒ Heating, air con‐

ditioning; Rep. gr. 87 ; Refrig‐

erant circuit (vehicle-specific

Workshop Manual).

♦ Actuation of air conditioner compres‐ – Extract refrigerant from re‐

sor not OK ⇒ Vehicle diagnostic tester,

“Guided Fault Finding” function for air

conditioner, air conditioner compres‐

sor and battery regulation .

frigerant circuit.

•

If quantity of refrigerant ex‐

tracted is substantially less

than specified capacity:

♦ Not enough refrigerant in circuit

– Locate leak with leak detec‐

tor and repair it.

♦ Expansion valve for evaporator in air

conditioning unit defective.

•

High pressure normal

low pressure too low (below

specified value)

– Re-charge refrigerant circuit.

– Repeat test.

•

Required cooling output is

not attained at evaporator in

air conditioning unit.

•

If amount of refrigerant ex‐

tracted roughly corresponds

to specified capacity:

– Renew expansion valve for

evaporator in air conditioning

unit.

– Re-charge refrigerant circuit.

– Repeat test.

On a vehicle with a shut-off

valve upstream of the evapo‐

rator in the air conditioning unit

(e.g. -N516- or -N541- (de‐

pending on vehicle) ⇒ Heating,

air conditioning; Rep. gr. 87 ;

Refrigerant circuit (vehicle-

specific Workshop Manual).

♦ Actuation of air conditioner compres‐ – Extract refrigerant from re‐

sor not OK ⇒ Vehicle diagnostic tester,

“Guided Fault Finding” function for air

conditioner, air conditioner compres‐

sor and battery regulation .

frigerant circuit.

•

The quantity of refrigerant

extracted is much less than

the specified capacity (con‐

tinue in same way as a vehi‐

cle without a shut-off valve

upstream of the evaporator

in the air conditioning unit)

♦ Not enough refrigerant in circuit

♦ Expansion valve for evaporator in air

conditioning unit defective.

•

High pressure normal

low pressure too low (below

specified value)

♦ Shut-off valve upstream of the evapo‐

rator in the air conditioning unit (e.g. -

N516- or -N541- (depending on vehi‐

cle) defective (closed) ⇒ Heating, air

conditioning; Rep. gr. 87 ; Refrigerant

circuit (vehicle-specific Workshop

Manual).

•

If amount of refrigerant ex‐

tracted roughly corresponds

to specified capacity:

•

The required cooling output

is not attained at the evap‐

orator in the air conditioning

unit and at the evaporator

for cooling the high-voltage

components.

– Check activation and opera‐

tion of shut-off valve up‐

stream of evaporator in air

conditioning unit (e.g. -N516-

or -N541- ) and shut-off valve

upstream of evaporator for

cooling high-voltage compo‐

nents (e.g. -N517- or -

N542- , depending on vehi‐

cle) ⇒ Heating, air condition‐

ing; Rep. gr. 87 ; Refrigerant

circuit (vehicle-specific

Workshop Manual).

– Renew expansion valve up‐

stream of evaporator in air

conditioning unit.

– Replace expansion valve (or

restrictor) upstream of the

evaporator for cooling the

high-voltage components.

– Re-charge refrigerant circuit.

– Repeat test.

238

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

♦ If no fault is found for this problem, clean refrigerant circuit (by

flushing with refrigerant R134a ⇒ page 100 or blowing out with

compressed air and nitrogen ⇒ page 95 ). Constriction or

blockage in the refrigerant circuit may also lead to one of these

problems.

♦ Depending on vehicle, check measured values of evaporator

output temperature sender - G263- and, if fitted, of tempera‐

ture sensor before evaporator for hybrid battery - G756- and

of temperature sensor after evaporator for hybrid battery -

G757- as well as activation of air conditioner compressor via

corresponding control units, e.g. control unit for air condition‐

ing compressor - J842- by battery regulation control unit -

J840- or by air conditioner operating and display unit

( Climatronic control unit - J255- ) ⇒ Vehicle diagnostic tester

in “Guided Fault Finding” mode for air conditioner and battery

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

erant circuit (vehicle-specific Workshop Manual) and ⇒ Cur‐

rent flow diagrams, Electrical fault finding and Fitting locations.

♦ Incorrect measured values from -G263- (or e.g. -G756- / -

G757- ) can also cause problems with the cooling output, or

the evaporator in the air conditioning unit may ice up ⇒ Vehicle

diagnostic tester in “Guided Fault Finding” mode for air con‐

ditioner and battery regulation and ⇒ Heating, air conditioning;

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

Manual).

♦ If, e.g. after renewing the expansion valve, operation of the air

conditioning system is not OK when the test is repeated (re-fit

old expansion valve), clean the refrigerant circuit (flush with

refrigerant R134a ⇒ page 100 or blow out with compressed air

and nitrogen ⇒ page 95 ). Then renew the air conditioner com‐

pressor and receiver/desiccant cartridge.

♦ If a temperature sensor is faulty, the evaporator may ice up

although the quantity of refrigerant in the circuit is OK.

♦ If the expansion valve at the evaporator in the air conditioning

unit (or e.g. -N516- / -N541- , depending on vehicle) is defec‐

tive (i.e. is permanently closed or does not open sufficiently),

the air conditioner compressor is activated to maximum output

and the low pressure drops to the value in the graph or below

(air conditioner compressor draws off refrigerant from low-

pressure side). However, because no refrigerant can flow via

the expansion valve, the cooling output is not attained and the

high pressure may also not increase or only increase slightly

since there is no energy exchange ⇒ Vehicle diagnostic tester

in “Guided Fault Finding” mode for air conditioner and battery

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

erant circuit (vehicle-specific Workshop Manual) and ⇒ Heat‐

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

Checking cooling output (vehicle-specific Workshop Manual).

8. Checking pressures

239

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

Air conditioner with refrigerant R134a - Edition 11.2018

♦ The evaporator in the air conditioning unit has a higher output

than the evaporator for cooling the high-voltage components

(e.g. in the battery cooling module or heat exchanger for high-

voltage battery, depending on vehicle). The shut-off valve (e.g.

refrigerant shut-off valve 2 for hybrid battery - N517- on the

expansion valve in the battery cooling module or refrigerant

shut-off valve for high-voltage battery heat exchanger -

N542- ) is activated by the battery regulation control unit - A2-

or air conditioner operating and display unit ( Climatronic

control unit - AX1- ) when the battery reaches or exceeds a

certain temperature, depending on the type of cooling used for

the drive battery - J840- / hybrid battery unit - J255- (hybrid

battery); energy exchange via the evaporator for cooling the

high-voltage components (in the battery cooling module or

heat exchanger for high-voltage battery) is not increased or

only slightly increased ⇒ Vehicle diagnostic tester in “Guided

Fault Finding” mode for air conditioner and battery regulation ,

⇒ 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 .

Possible deviation from speci‐

fication

Possible causes of fault

Fault elimination

On a vehicle with a shut-off

valve upstream of the evapo‐

rator in the air conditioning unit

(e.g. -N516- or -N541- (de‐

pending on vehicle) ⇒ Heating,

air conditioning; Rep. gr. 87 ;

Refrigerant circuit (vehicle-

specific Workshop Manual).

♦ Actuation of air conditioner compres‐ – Extract refrigerant from re‐

sor not OK ⇒ Vehicle diagnostic tester,

“Guided Fault Finding” function for air

conditioner, air conditioner compres‐

sor and battery regulation .

frigerant circuit.

•

If the amount of refrigerant

extracted is significantly less

than the specified capacity:

♦ Not enough refrigerant in circuit

– Locate leak with leak detec‐

tor and repair it.

♦ Expansion valve for evaporator in air

conditioning unit defective.

•

High pressure normal

low pressure too low (below

specified value)

– Re-charge refrigerant circuit.

– Repeat test.

♦ Shut-off valve upstream of the evapo‐

rator in the air conditioning unit (e.g. -

N516- or -N541- (depending on vehi‐

cle) defective (closed) ⇒ Heating, air

conditioning; Rep. gr. 87 ; Refrigerant

circuit (vehicle-specific Workshop

Manual).

•

The required cooling output

is not attained solely at the

evaporator in the air condi‐

tioning unit (the cooling out‐

put is OK at the evaporator

for cooling the high-voltage

components).

•

If amount of refrigerant ex‐

tracted roughly corresponds

to specified capacity:

– Check activation and opera‐

tion of shut-off valve (e.g. -

N516- or -N541- , depending

on vehicle); renew expan‐

sion valve at evaporator in air

conditioning unit if no fault is

found ⇒ Heating, air condi‐

tioning; Rep. gr. 87 ; Refrig‐

erant circuit (vehicle-specific

Workshop Manual).

– Re-charge refrigerant circuit.

– Repeat test.

240

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

Possible deviation from speci‐

fication

Possible causes of fault

Fault elimination

•

High pressure normal

On vehicles with a battery cooling module – Check operation and activa‐

♦ Actuation or operation of refrigerant

shut-off valve 2 for hybrid battery -

N517- , of a control motor, blower or

temperature sensor in or at battery

cooling module not OK.

tion of the components for

cooling the high-voltage

components ⇒ Vehicle diag‐

nostic tester in “Guided Fault

Finding” mode for air condi‐

tioner, air conditioner com‐

pressor and battery regula‐

tion

•

low pressure too low (below

specified value)

•

The required cooling output

is not attained solely at the

evaporator for cooling the

high-voltage components

(the cooling output is OK at

the evaporator in the air

conditioning unit).

♦ Constriction or blockage in the refrig‐

erant line to or from the expansion

valve at the battery cooling module

– Check refrigerant lines

♦ Expansion valve for evaporator for

cooling high-voltage components de‐

fective

– Extract refrigerant from re‐

frigerant circuit.

♦ Not enough refrigerant in circuit

– Depending on vehicle, fit -

N517- in place of expansion

valve ⇒ Heating, air condi‐

tioning; Rep. gr. 87 ; Refrig‐

erant circuit (vehicle-specific

Workshop Manual).

On vehicles with a heat exchanger for

high-voltage battery

– Check restrictor in refriger‐

ant line to heat exchanger for

high-voltage battery and

♦ Activation or operation of shut-off valve

(e.g. refrigerant shut-off valve for high-

voltage battery heat exchanger -

clean or renew, if necessary.

N542- , faulty refrigerant pump or fault – Re-charge refrigerant circuit.

in refrigerant circuit for high-voltage

components ⇒ Heating, air condition‐ – Repeat test.

ing; Rep. gr. 87 ; Refrigerant circuit

(vehicle-specific Workshop Manual).

♦ Constriction or obstruction in the refrig‐

erant lines leading to or from the heat

exchanger for high-voltage battery

♦ Restrictor in the refrigerant line to the

heat exchanger for high-voltage bat‐

tery blocked

♦ Not enough refrigerant in circuit

8. Checking pressures

241

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

Air conditioner with refrigerant R134a - Edition 11.2018

Note

♦ On vehicles with battery cooling module, the refrigerant shut-

off valve 2 for hybrid battery - A2- is currently activated by the

battery regulation control unit - N517- in order to cool the drive

battery - J840- (hybrid battery) only when the battery reaches

a certain temperature. If air conditioning mode has not already

been activated at this point, the electrical air conditioner com‐

pressor - V470- is actuated via the control unit for air condi‐

tioning compressor - J842- by -J840- . The temperature of the

air upstream and downstream of the evaporator in the battery

cooling module is determined by -J840- . If it is established

that the cooling is not sufficient, this is stored in -J840- ⇒ Ve‐

hicle diagnostic tester in “Guided Fault Finding” mode for air

conditioner, air conditioner compressor and battery regulation

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

cuit (vehicle-specific Workshop Manual).

♦ On vehicles with a battery cooling module, the temperature of

the air (and thus the cooling output of the evaporator) in the

battery cooling module is determined by way of built-in tem‐

perature sensors (at present it cannot be measured with a

thermometer during operation) and can only be checked using

the Guided Fault Finding routine ⇒ Vehicle diagnostic tester,

“Guided Fault Finding” function for air conditioner, air condi‐

tioner compressor and battery regulation .

♦ On vehicles with a battery cooling module, observe additional

information ⇒ page 239 .

♦ On some vehicles with a heat exchanger for high-voltage bat‐

tery (e.g. Audi A3 e-tron; components may have a different

designation on other vehicles), the refrigerant shut-off valve

for high-voltage battery heat exchanger - A2- is no longer ac‐

tivated by the operating unit ( Climatronic control unit - J1050- )

above a certain temperature in order to cool the high-voltage

components, e.g. the drive battery - N542- and the high-volt‐

age battery charger control unit - J255- ( -N542- is open when

the system is de-energised. If air conditioning mode has not

already been activated at this point, the operating unit -V470-

actuates the electrical air conditioner compressor - J842- via

the control unit for air conditioning compressor - J255- . Other

components in this circuit must be actuated (e.g. refrigerant

circulation pump 2 - V178- and solenoid valve 1 - N88- ) and

the refrigerant must flow through the heat exchanger for high-

voltage battery to ensure that the refrigerant actually cools the

high-voltage components. If it is established that the cooling

of the high-voltage components is not sufficient, this is stored

in various control units ⇒ Vehicle diagnostic tester in “Guided

Fault Finding” mode for air conditioner, air conditioner com‐

pressor and battery regulation , ⇒ Heating, air conditioning;

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

Manual) and ⇒ Rep. gr. 19 ; Cooling system/coolant; Con‐

nection diagram - coolant hoses .

♦ If no fault is found for this problem, clean refrigerant circuit (by

flushing with refrigerant R134a ⇒ page 100 or blowing out with

compressed air and nitrogen ⇒ page 95 ). Constriction or

blockage in the refrigerant circuit may also lead to one of these

problems.

242

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

Possible devia‐ Possible causes of

Fault elimination

tion from specifi‐

cation

fault

On a vehicle with ♦ Air conditioner

– Check actuation

and operation of the

air conditioner com‐

pressor and repair if

necessary ⇒ Vehi‐

cle diagnostic test‐

er, “Guided Fault

Finding” function

for air conditioner

and battery regula‐

tion

a shut-off valve

upstream of the

evaporator in the

air conditioning

unit (e.g. -N516-

or -N541- (de‐

pending on vehi‐

cle) ⇒ Heating,

air conditioning;

Rep. gr. 87 ; Re‐

frigerant circuit

(vehicle-specific

Workshop Man‐

ual).

compressor is not

activated or driv‐

en.

♦ Shut-off valve -

N516- or -N541-

(depending on

vehicle) faulty

(blocked) ⇒

Heating, air con‐

ditioning; Rep.

gr. 87 ; Refriger‐

ant circuit (vehi‐

cle-specific

– Check activation

and operation of

shut-off valve (e.g. -

N516- or -N541- ,

depending on vehi‐

cle); renew expan‐

sion valve at evap‐

orator in air condi‐

tioning unit if no

fault is found ⇒

Workshop Man‐

ual).

•

High pres‐

sure does not

rise or only

rises slightly

above the

pressure with

the engine

stopped.

Heating, air condi‐

tioning; Rep. gr.

87 ; Refrigerant cir‐

cuit (vehicle-specif‐

ic Workshop Man‐

ual).

•

Low pressure

does not drop

or only drops

slightly.

Required

cooling out‐

put is not at‐

tained in

evaporator in

air condition‐

ing unit (and

in evaporator

for cooling

high-voltage

components)

♦ Constriction or

blockage in re‐

frigerant circuit

(e.g. in refrigerant

line between

– Clean refrigerant

circuit (flush with re‐

frigerant R134a

⇒ page 100 or blow

out with com‐

service connec‐

tion on low-pres‐

sure side and air

pressed air and ni‐

trogen ⇒ page 95 ).

conditioner com‐ – Renew hose or pipe

pressor).

if kinked or constric‐

ted.

♦ Air conditioner

compressor de‐

fective

– Renew air condi‐

tioner compressor.

8. Checking pressures

243

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

Air conditioner with refrigerant R134a - Edition 11.2018

Possible deviation from spec‐

ification

Possible causes of fault

Fault elimination

On a vehicle without a shut-off ♦ Activation or operation of air con‐ – Check actuation and operation of the

valve upstream of the evapo‐

rator in the air conditioning

unit (e.g. -N516- or -N541-

(depending on vehicle) ⇒

Heating, air conditioning;

Rep. gr. 87 ; Refrigerant cir‐

cuit (vehicle-specific Work‐

shop Manual).

ditioner compressor not OK

air conditioner compressor and re‐

pair if necessary ⇒ Vehicle diagnos‐

tic tester, “Guided Fault Finding”

function for air conditioner and bat‐

tery regulation

♦ Constriction or blockage in refrig‐

erant circuit

♦ Expansion valve defective

– Run hand over refrigerant circuit to

check for differences in temperature.

•

High pressure increases

above specification

•

If there is a difference in temperature

at one component:

Low pressure drops quick‐

ly to specified value

– Renew hose or pipe if kinked or con‐

stricted.

Required cooling output is

not attained in evaporator

in air conditioning unit (and

in evaporator for cooling

high-voltage components)

– In the event of clogging, clean refrig‐

erant circuit (flush with refrigerant

R134a ⇒ page 100 or blow out with

compressed air and nitrogen

⇒ page 95 ).

– Re-charge refrigerant circuit.

– Repeat test.

•

If operation is not OK and no fault is

found:

– Clean refrigerant circuit (flush with

refrigerant R134a ⇒ page 100 or

blow out with compressed air and ni‐

trogen ⇒ page 95 ).

– Re-charge refrigerant circuit.

– Repeat test if operation is not OK:

– Renew expansion valve upstream of

evaporator in air conditioning unit

and receiver.

On a vehicle with a shut-off ♦ Activation or operation of air con‐ – Check activation and operation of air

valve upstream of the evapo‐

rator in the air conditioning

unit (e.g. -N516- or -N541-

(depending on vehicle) ⇒

Heating, air conditioning;

Rep. gr. 87 ; Refrigerant cir‐

cuit (vehicle-specific Work‐

shop Manual).

ditioner compressor or shut-off

valve (e.g. -N516- or -N541- , de‐

pending on vehicle) faulty. ⇒

Heating, air conditioning; Rep.

gr. 87 ; Refrigerant circuit (vehi‐

cle-specific Workshop Manual).

conditioner compressor and shut-off

valves (e.g. -N516- ) ⇒ Vehicle di‐

agnostic tester in “Guided Fault

Finding” mode for air conditioner and

battery regulation and ⇒ Heating, air

conditioning; Rep. gr. 87 ; Refriger‐

ant circuit (vehicle-specific Work‐

shop Manual).

♦ Constriction or blockage in refrig‐

erant circuit

•

High pressure increases

above specification

– Perform further testing as described

for vehicles without shut-off valve

upstream of evaporator.

♦ Expansion valve defective

low pressure quickly drops

to specified value,

Required cooling output is

not attained in evaporator

in air conditioning unit (and

in evaporator for cooling

high-voltage components)

244

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

♦ If the operation of the air conditioner is not OK when the test

is repeated, renew the expansion valve and receiver (and -

N516- / -N541- if fitted) ⇒ Heating, air conditioning; Rep. gr.

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

♦ In this case, the evaporator may ice up although the amount

of refrigerant in the refrigerant circuit is OK.

♦ If the expansion valve at the evaporator in the air conditioning

unit or the shut-off valve (e.g. -N516- or -N541- ) is defective

(is permanently closed or does not open sufficiently), the air

conditioner compressor is activated to maximum output and

the low pressure drops to the specified value or below (air

conditioner compressor draws off refrigerant from low-pres‐

sure side). However, because no refrigerant (or only a small

amount) can flow via the expansion valve (the corresponding

shut-off valve), the cooling output is not attained and the high

pressure may also not increase or only increase slightly since

there is no energy exchange ⇒ Vehicle diagnostic tester in

“Guided Fault Finding” mode for air conditioner and battery

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

erant circuit (vehicle-specific Workshop Manual) and ⇒ Heat‐

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

Checking cooling output (vehicle-specific Workshop Manual).

♦ If a vehicle has a battery cooling module and the expansion

valve on the evaporator in the battery cooling module is de‐

fective (or refrigerant shut-off valve 2 for hybrid battery - N517-

is not operating or is not actuated properly), or if the expansion

valve is permanently closed or does not open sufficiently, the

air conditioner compressor is also actuated to maximum out‐

put (the required temperatures in the battery cooling module

are not reached). The pressure on the low-pressure side then

only drops to or below the specified value if no cooling output

is requested in the air conditioning unit at the same time (the

shut-off valve upstream of the evaporator in the air condition‐

ing unit, e.g. -N516- , is activated and closed). The air condi‐

tioner compressor draws off the refrigerant from the low-

pressure side of both evaporators. However, as no refrigerant

can flow via the expansion valve in the air conditioning unit

(e.g. -N516- ) and the cooling output is not reached in the bat‐

tery cooling module (fault in area of battery cooling module),

the electric air conditioner compressor is activated at a higher

speed. However, as no more refrigerant can flow, the pressure

on the low-pressure side drops below the specified value and

the high pressure may also not increase or only increase

slightly since there is no energy exchange ⇒ Vehicle diag‐

nostic tester in “Guided Fault Finding” mode for air conditioner

and battery regulation , ⇒ Heating, air conditioning; Rep. gr.

87 ; Refrigerant circuit (vehicle-specific Workshop Manual)

and ⇒ Heating, air conditioning; Rep. gr. 00 ; Repair instruc‐

tions; Checking cooling output (vehicle-specific Workshop

Manual).

8. Checking pressures

245

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

Air conditioner with refrigerant R134a - Edition 11.2018

♦ On vehicles with a high-voltage battery heat exchanger, if the

restrictor installed in the refrigerant line to the high-voltage

battery heat exchanger is blocked or the shut-off valve (e.g.

refrigerant shut-off valve for high-voltage battery heat ex‐

changer - N542- on the Audi A3 e-tron) installed in this line is

faulty, permanently closed or does not open far enough, the

air conditioner compressor is also activated to maximum out‐

put (the required temperatures in the refrigerant circuit are not

reached with the high-voltage battery heat exchanger). The

pressure on the low-pressure side then only drops to or below

the specified value if no cooling output is requested in the air

conditioning unit at the same time ( -N541- is activated and

closed, e.g. on the Audi A3 e-tron). The air conditioner com‐

pressor draws off the refrigerant from the low-pressure side of

both evaporators. However, because refrigerant cannot flow

via the expansion valve into the air conditioning unit (via the

shut-off valve, e.g. -N541- ) and the cooling output in the high-

voltage battery heat exchanger is not reached, the electric air

conditioner compressor is activated at a higher speed. How‐

ever, as no more refrigerant can flow, the pressure on the low-

pressure side drops below the specified value and the high

pressure may also not increase or only increase slightly since

there is no energy exchange ⇒ Vehicle diagnostic tester in

“Guided Fault Finding” mode for air conditioner and battery

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

erant circuit (vehicle-specific Workshop Manual) and ⇒ Heat‐

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

Checking cooling output (vehicle-specific Workshop Manual).

The same applies if a fault occurs in the coolant circuit where

the high-voltage battery heat exchanger is installed (e.g. cool‐

ant circulation pump 2 - V178- or solenoid valve 1 - N88- (on

Audi A3 e-tron) are not activated correctly or are faulty). Al‐

though the high-voltage battery heat exchanger is cooled, the

coolant does not reach the high-voltage components which

need to be cooled ⇒ Heating, air conditioning; Rep. gr. 87 ;

Coolant circuit (vehicle-specific Workshop Manual) and ⇒

Rep. gr. 19 ; Cooling system/coolant; Connection diagram -

coolant hoses .

♦ As the cooling output of the evaporator for cooling the high-

voltage battery is less than that of the evaporator in the air

conditioning unit, the required temperature in the evaporator

for cooling the high-voltage battery may still be reached when

there is not enough refrigerant in the circuit, but the required

temperature will no longer be reached at the evaporator in the

air conditioning unit (although the air conditioner compressor

is activated at a higher speed).

♦ If there is too much refrigerant oil in the circuit, also discharge

(flush) the air conditioner compressor and renew the receiver/

desiccant cartridge. After cleaning the refrigerant circuit (flush‐

ing with refrigerant R134a ⇒ page 100 or blowing out with

compressed air and nitrogen ⇒ page 95 ), add the correct

amount of refrigerant oil to the circuit (to the air conditioner

compressor) ⇒ page 333 .

246

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

Possible deviation from speci‐

fication

Possible causes of fault

Fault elimination

•

High and low pressure nor‐ ♦ Activation or operation of air condition‐ – Check activation of air con‐

mal at first, but after a while:

er compressor or shut-off valve (e.g. -

N516- or -N541- , depending on vehi‐

cle) faulty ⇒ Heating, air conditioning;

Rep. gr. 87 ; Refrigerant circuit (vehi‐

cle-specific Workshop Manual).

ditioner compressor and

shut-off valve (e.g. -N516- or

-N541- ) ⇒ Vehicle diagnos‐

tic tester in “Guided Fault

Finding” mode for air condi‐

tioner and battery regula‐

tion .

High pressure rises above

specified value

Low pressure drops to

specified value or below

♦ Moisture in refrigerant circuit

Required cooling output is

not attained in evaporator in

air conditioning unit (and in

evaporator for cooling high-

voltage components)

– Clean refrigerant circuit

(flush with refrigerant R134a

⇒ page 100 or blow out with

compressed air and nitrogen

⇒ page 95 ).

– Renew receiver with dryer.

•

High and low pressure nor‐

mal at first

– Evacuate refrigerant circuit

for at least 3 hours.

After driving for a while, low

pressure drops below

specified value (evaporator

in air conditioning unit ices

up)

– Re-charge refrigerant circuit.

– Repeat test.

Note

♦ It is not initially necessary to clean the refrigerant circuit (flush

with refrigerant R134a ⇒ page 100 or blow out with com‐

pressed air and nitrogen ⇒ page 95 ) when this problem

occurs. Normally, there is only a small quantity of moisture in

the system which can be removed by lengthy evacuation.

♦ If an issue involving moisture in the refrigerant circuit only oc‐

curs after a lengthy operating period or only infrequently (low

pressure drops below specified value and evaporator ices up),

it is sufficient to renew the dryer in the receiver (adjust quantity

of refrigerant oil). Subsequently, evacuate refrigerant circuit

for at least 3 hours.

♦ In this case, the evaporator may ice up although the amount

of refrigerant in the refrigerant circuit is OK.

♦ A faulty evaporator output temperature sender - G263- and/

or, if fitted, temperature sensor after evaporator for hybrid bat‐

tery - G757- (depending on vehicle) may also cause the re‐

frigerant circuit to ice up. If this problem occurs, also observe

the measured value for -G263- and -G757- (e.g. on vehicles

with a battery cooling module) ⇒ Vehicle diagnostic tester; in

“Guided Fault Finding” mode for air conditioner, ⇒ Heating,

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

cific Workshop Manual) and ⇒ Heating, air conditioning; Rep.

gr. 00 ; Repair instructions; Checking cooling output (vehicle-

specific Workshop Manual).

8. Checking pressures

247

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

Air conditioner with refrigerant R134a - Edition 11.2018

Possible deviation from speci‐

Possible causes of fault

Fault elimination

fication

•

High pressure normal

Low pressure too low

♦ Activation or operation of air condition‐ – Check activation and opera‐

er compressor or, if fitted, shut-off

valves (e.g. -N516- , -N517- , -N541- or

-N542- , depending on vehicle) faulty

⇒ Heating, air conditioning; Rep. gr.

87 ; Refrigerant circuit (vehicle-specific

Workshop Manual).

tion of air conditioner com‐

pressor and, if fitted, shut-off

valves (e.g. -N516- and -

N517- ) ⇒ Vehicle diagnostic

tester in “Guided Fault Find‐

ing” mode for air conditioner

and battery regulation and ⇒

Heating, air conditioning;

Rep. gr. 87 ; Refrigerant cir‐

cuit (vehicle-specific Work‐

shop Manual).

Required cooling output is

not attained in evaporator in

air conditioning unit (and in

evaporator for cooling high-

voltage components)

♦ Expansion valve in air conditioning unit

or, if fitted, in battery cooling module

defective.

♦ Expansion valve in the air conditioning

unit faulty or restrictor in the refrigerant

line to the heat exchanger for high-volt‐

age battery blocked (if available).

– Clean refrigerant circuit

(flush with refrigerant R134a

⇒ page 100 or blow out with

compressed air and nitrogen

⇒ page 95 ) (not always nec‐

essary, refer to notes).

♦ Air conditioner compressor defective

– Renew expansion valve for

evaporator in air conditioning

unit and for receiver/dryer.

– If fitted, renew expansion

valve for evaporator in bat‐

tery cooling module or clean/

renew refrigerant line with re‐

strictor to the heat exchanger

for high-voltage battery.

– Re-charge refrigerant circuit.

– Repeat test if operation is not

OK:

– Renew air conditioner com‐

pressor.

– Re-charge refrigerant circuit.

– Repeat test.

248

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

♦ If the fault “High pressure normal, low pressure too low” oc‐

curs, please note that the evaporator in the air conditioning

unit may ice up although the amount of refrigerant in the circuit

is OK.

♦ If the problem is with the air conditioner compressor (the air

conditioner compressor is actuated at excessively high speed

by the air conditioner compressor regulating valve - J842- ),

the refrigerant circuit does not have to be cleaned (by flushing

with refrigerant R134a ⇒ page 100 or blowing out with com‐

pressed air and nitrogen ⇒ page 95 ). In this case it is sufficient

to renew the air conditioner compressor (observe quantity of

refrigerant oil in compressor and adjust if necessary).

♦ On vehicles with a battery cooling module, if the expansion

valve for the evaporator in the air conditioning unit or the ex‐

pansion valve for the evaporator in the battery cooling module

is defective (permanently closed or does not open sufficiently),

the air conditioner compressor is also actuated to maximum

output and the pressure on the low-pressure side drops to the

value in the graph or below (the air conditioner compressor

draws off refrigerant from the low-pressure side). As refriger‐

ant cannot however flow via the defective expansion valve, the

cooling output is not attained in the downstream evaporator

and the high pressure may either not increase or only increase

slightly due to the absence of energy conversion. However,

the air conditioner compressor may be activated at a higher

speed, as the required cooling output is not attained in one

evaporator. This also applies if operation or activation of a

shut-off valve (e.g. refrigerant shut-off valve 1 for hybrid bat‐

tery - N516- or refrigerant shut-off valve 2 for hybrid battery -

N517- , depending on vehicle) is not OK ⇒ Vehicle diagnostic

tester; in “Guided Fault Finding” mode for air conditioner, ⇒

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

hicle-specific Workshop Manual) and ⇒ Heating, air condi‐

tioning; Rep. gr. 00 ; Repair instructions; Checking cooling

output (vehicle-specific Workshop Manual).

♦ On vehicles with a high-voltage battery heat exchanger, if the

expansion valve for the evaporator in the air conditioning unit

is defective (permanently closed or does not open far enough)

or the restrictor in the refrigerant line to the high-voltage bat‐

tery heat exchanger is blocked, the air conditioner compressor

is also activated to maximum output and the pressure on the

low-pressure side drops to the value in the graph or below (the

air conditioner compressor draws off refrigerant from the low-

pressure side). However, as refrigerant cannot flow via the

defective expansion valve or blocked restrictor, the cooling

output is not attained in the downstream evaporator and the

high pressure may either not increase or only increase slightly

since there is no energy exchange. However, the air condi‐

tioner compressor may be activated at a higher speed, as the

required cooling output is not attained in one evaporator. This

also applies if operation or activation of a shut-off valve (e.g.

refrigerant shut-off valve for heater and air conditioner unit -

N541- or refrigerant shut-off valve for high-voltage battery heat

exchanger - N542- , depending on vehicle) or a component

installed in the refrigerant circuit for high-voltage components

(e.g. coolant circulation pump 2 - V178- or solenoid valve 1 -

N88- on Audi A3 e-tron, depending on vehicle) is not OK

⇒ Vehicle diagnostic tester; in “Guided Fault Finding” mode for

air conditioner, ⇒ Rep. gr. 19 ; Cooling system/coolant; Con‐

nection diagram - coolant hoses and ⇒ Heating, air condi‐

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

Workshop Manual).

8. Checking pressures

249

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

Air conditioner with refrigerant R134a - Edition 11.2018

♦ Check the measured values for the evaporator output tem‐

perature sender - G263- (and if applicable the measured

values for the temperature sensor before evaporator for hybrid

battery - G756- and temperature sensor after evaporator for

hybrid battery - G757- , depending on vehicle) as well as ac‐

tivation of the air conditioner compressor by the battery regu‐

lation control unit - J840- , the air conditioner operating unit

( Climatronic control unit - J255- ) / operating and display unit

for front air conditioning system - E87- or thermal management

control unit - J1024- (depending on vehicle). If the measured

value of -G263- (or -G756- / -G757- , depending on vehicle)

or activation of the air conditioner compressor is not OK, the

evaporator may ice up or the required cooling output is not

attained ⇒ Vehicle diagnostic tester; in “Guided Fault Finding”

mode for air conditioner, ⇒ Heating, air conditioning; Rep. gr.

87 ; Refrigerant circuit (vehicle-specific Workshop Manual)

and ⇒ Heating, air conditioning; Rep. gr. 00 ; Repair instruc‐

tions; Checking cooling output (vehicle-specific Workshop

Manual).

250

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

Possible deviation from speci‐

fication

Possible causes of fault

Fault elimination

•

High pressure normal or too ♦ Activation or operation of air condition‐ – Check activation and opera‐

high

er compressor not OK

tion of air conditioner com‐

pressor and, if fitted, these

shut-off valves ( -N516- , -

N517- , -N541- and -N542- ,

depending on vehicle) ⇒ Ve‐

hicle diagnostic tester in

“Guided Fault Finding” mode

for air conditioner and bat‐

tery regulation and ⇒ Heat‐

ing, air conditioning; Rep. gr.

87 ; Refrigerant circuit (vehi‐

cle-specific Workshop Man‐

ual).

•

Low pressure too high

♦ Depending on refrigerant circuit ver‐

sion, activation or operation of one of

these shut-off valves ( -N516- , -N517- ,

-N541- or -N542- , depending on vehi‐

cle) is not OK ⇒ Heating, air condition‐

ing; Rep. gr. 87 ; Refrigerant circuit

(vehicle-specific Workshop Manual).

Noise from air conditioner

compressor (particularly af‐

ter being switched on)

•

The required cooling output

is not attained in the evap‐

orator in the air conditioning

unit and / or in the evapora‐

♦ Too much refrigerant in circuit

tor for cooling the high-volt‐ ♦ Expansion valve defective

age components.

♦ Air conditioner compressor defective

– Extract refrigerant from re‐

frigerant circuit.

•

The quantity of refrigerant

extracted corresponds

roughly to the actual capaci‐

ty.

– Renew expansion valve for

evaporator in air conditioning

unit and for receiver/dryer.

– Renew expansion valve with

-N517- .

– Check restrictor in refriger‐

ant line to heat exchanger for

high-voltage battery and

clean or renew, if necessary.

– Re-charge refrigerant circuit.

– Repeat test if operation is not

OK.

– Renew air conditioner com‐

pressor.

•

If quantity of refrigerant ex‐

tracted is significantly great‐

er than specified capacity:

– Re-charge refrigerant circuit.

– Repeat test.

8. Checking pressures

251

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

Air conditioner with refrigerant R134a - Edition 11.2018

Note

♦ This fault may also be caused by too much refrigerant oil in

the circuit. Overfilling with refrigerant oil may occur if, for ex‐

ample, the air conditioner compressor has been renewed

without adjusting the quantity of refrigerant oil.

♦ On vehicles with a battery cooling module, if the expansion

valve for the evaporator in the air conditioning unit or the ex‐

pansion valve for the evaporator in the battery cooling module

is defective (permanently closed or does not open sufficiently),

the air conditioner compressor is also actuated to maximum

output and the pressure on the low-pressure side drops to the

value in the graph or below (the air conditioner compressor

draws off refrigerant from the low-pressure side). As refriger‐

ant cannot however flow via the defective expansion valve, the

cooling output is not attained in the downstream evaporator

and the high pressure may either not increase or only increase

slightly due to the absence of energy conversion. However,

the air conditioner compressor may be activated at a higher

speed, as the required cooling output is not attained in one

evaporator. This also applies if operation or activation of a

shut-off valve (e.g. refrigerant shut-off valve 1 for hybrid bat‐

tery - N516- or refrigerant shut-off valve 2 for hybrid battery -

N517- , depending on vehicle) is not OK ⇒ Vehicle diagnostic

tester; in “Guided Fault Finding” mode for air conditioner and

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

(vehicle-specific Workshop Manual).

♦ On vehicles with a high-voltage battery heat exchanger, if the

expansion valve for the evaporator in the air conditioning unit

is defective (permanently closed or does not open far enough)

or the restrictor in the refrigerant line to the high-voltage bat‐

tery heat exchanger is blocked, the air conditioner compressor

is also activated to maximum output and the pressure on the

low-pressure side drops to the value in the graph or below (the

air conditioner compressor draws off refrigerant from the low-

pressure side). However, as refrigerant cannot flow via the

defective expansion valve or blocked restrictor, the cooling

output is not attained in the downstream evaporator and the

high pressure may either not increase or only increase slightly

since there is no energy exchange. However, the air condi‐

tioner compressor may be activated at a higher speed, as the

required cooling output is not attained in one evaporator. This

also applies if operation or activation of refrigerant shut-off

valve for heater and air conditioner unit - N541- , refrigerant

shut-off valve for high-voltage battery heat exchanger - N542-

(e.g. on Audi A3 e-tron) or a component installed in the refrig‐

erant circuit for high-voltage components (e.g. coolant circu‐

lation pump 2 - V178- or solenoid valve 1 - N88- on Audi A3

e-tron) is not OK ⇒ Vehicle diagnostic tester; in “Guided Fault

Finding” mode for air conditioner, ⇒ Rep. gr. 19 ; Cooling

system/coolant; Connection diagram - coolant hoses and ⇒

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

hicle-specific Workshop Manual).

252

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

Possible deviation from speci‐

fication

Possible causes of fault

Fault elimination

•

High and low pressure nor‐ ♦ Activation or operation of air condition‐ – Check activation and opera‐

mal

er compressor not OK

tion of air conditioner com‐

pressor and, if fitted, these

shut-off valves (e.g. -N516- ,

-N517- , -N541- and -N542- )

⇒ Vehicle diagnostic tester

in “Guided Fault Finding”

mode for air conditioner and

battery regulation and ⇒

Heating, air conditioning;

Rep. gr. 87 ; Refrigerant cir‐

cuit (vehicle-specific Work‐

shop Manual).

•

Required cooling output is ♦ Depending on refrigerant circuit ver‐

not attained in evaporator in

air conditioning unit (and in

evaporator for cooling high-

voltage components)

sion, activation or operation of one of

these shut-off valves (e.g. -N516- , -

N517- , -N541- or -N542- , depending

on vehicle) is not OK ⇒ Heating, air

conditioning; Rep. gr. 87 ; Refrigerant

circuit (vehicle-specific Workshop

Manual).

♦ Too much refrigerant in circuit

♦ Expansion valve defective

– Discharge refrigerant circuit.

– Clean refrigerant circuit

(flush with refrigerant R134a

⇒ page 100 or blow out with

compressed air and nitrogen

⇒ page 95 ).

– Add correct quantity of refrig‐

erant oil to circuit (refer to

note).

•

High and low pressure nor‐

mal

Noise from air conditioner

compressor (particularly af‐

ter being switched on)

– Re-charge refrigerant circuit.

– Repeat test if operation is not

OK:

•

Required cooling output is

not attained in evaporator in

air conditioning unit (and/or

in evaporator for cooling

high-voltage components)

– Renew expansion valve.

– Re-charge refrigerant circuit.

– Repeat test.

Note

♦ Overfilling with refrigerant oil may occur if, for example, the air

conditioner compressor has been renewed without adjusting

the quantity of refrigerant oil.

♦ If for example the expansion valve for the evaporator in the air

conditioning unit is defective (permanently open), the evapo‐

rator temperature (in the air conditioning unit) is no longer

regulated such that only refrigerant in gas form exits from the

evaporator. Under certain usage conditions, liquid droplets

may then be drawn in by the air conditioner compressor and

result in noise (liquid cannot be compressed).

♦ If there is too much refrigerant oil in the circuit, discharge the

air conditioner compressor and renew the receiver. After

cleaning the refrigerant circuit (flushing with refrigerant R134a

⇒ page 100 ), add the correct amount of refrigerant oil to the

circuit ⇒ page 333 .

8. Checking pressures

253

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

Air conditioner with refrigerant R134a - Edition 11.2018

8.6.2

Specifications for pressures in refriger‐

ant circuit on vehicles with heat pump

Note

♦ On vehicles with high-voltage system and heat pump (e.g.

Audi Q7 e-tron), non-return valves and electrically activated

valves are installed in the refrigerant circuit which regulate the

flow of refrigerant in the refrigerant circuit depending on the

current operating mode. There are different versions of these

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

circuit (vehicle-specific Workshop Manual) and ⇒ Vehicle di‐

agnostic tester in “Guided Fault Finding” mode.

♦ 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 op‐

erating modes. On these vehicles, the pressure in the refrig‐

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

via the pressure/temperature senders installed in the refriger‐

ant 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”).

♦ On these vehicles, the air conditioning system's refrigerant

circuit is used not only to cool the passenger compartment but

also to cool the hybrid battery unit - AX1- (via the high-voltage

system's coolant circuit) and heat the passenger compartment

via the heat pump function when ambient temperatures are

low. To operate these functions, various valves, pressure/

temperature senders and pumps in the refrigerant circuit and

the high-voltage system's coolant circuit must be correctly in‐

stalled and working properly ⇒ Heating, air conditioning; Rep.

gr. 87 ; Refrigerant circuit (vehicle-specific Workshop Man‐

ual), ⇒ Vehicle diagnostic tester in “Guided Fault Finding”

mode and ⇒ Engine, mechanics; Rep. gr. 19 ; Cooling sys‐

tem/coolant; Draining and filling cooling system .

♦ To locate the possible cause of a malfunction, various routines

have been stored in the basic setting of -J1024- ; these rou‐

tines activate the “Air conditioner cooling”, “Heat pump” and

“Cooling of high-voltage system components” functions ⇒ Ve‐

hicle diagnostic tester (“Guided Fault Finding”).

High-pressure side:

Increasing from initial pressure (when connecting pressure

gauges) up to max. 20 bar

Note

Depending on the layout of the service connection (high-pressure

side) and on the operating mode, it may only be possible to meas‐

ure the high pressure via the pressure/temperature senders in‐

stalled in the refrigerant circuit ⇒ Heating, air conditioning; Rep.

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

Low-pressure side:

Dropping from initial pressure (when connecting pressure

gauges) to a value between 1.5 and 2.3 bar absolute (depending

on cooling output required)

254

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

Air conditioner compressor speed:

Between 800 and 8600 rpm depending on cooling output required

(currently max. 5000 rpm with vehicle stationary)

8. Checking pressures

255

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

Air conditioner with refrigerant R134a - Edition 11.2018

Note

♦ The temperature of the air downstream of the evaporator, the

current air conditioner compressor speed and the refrigerant

pressure on the high-pressure side are displayed as meas‐

ured values by various control units depending on the vehicle

(e.g. by the thermal management control unit - J1024- , oper‐

ating and display unit for front air conditioning system - E87-

or Climatronic control unit - J255- ) ⇒ Heating, air conditioning;

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

Manual), and ⇒ Vehicle diagnostic tester in “Guided Fault

Finding” mode.

♦ If a very high cooling output is required (e.g. high ambient

temperature and high fresh air blower speed), the air condi‐

tioner compressor cannot initially set the pressure on the low-

pressure side to the necessary value (e.g. for a certain time

after switching on the air conditioner). When the vehicle is sta‐

tionary or only moving slowly (up to a speed of approx. 45 km/

h), the air conditioner compressor is not activated at the max‐

imum specified speed (of approx. 8500 rpm); the air condi‐

tioner compressor speed is limited to approx. 5000 rpm.

Limitation of the maximum permissible air conditioner com‐

pressor speed is only cancelled at vehicle speeds above

approx. 45 km/h. At an air conditioner compressor speed of

5000 rpm, with a high ambient temperature and a high fresh

air blower speed (unfavourable ambient conditions), the out‐

put (delivery volume) of the air conditioner compressor is not

initially sufficient to reduce the pressure on the low-pressure

side to the specified value. One way of checking the control

action of the air conditioner compressor under these condi‐

tions is to activate 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 for air conditioner and battery regulation,

and ⇒ Heating, air conditioning; Rep. gr. 00 ; Repair instruc‐

tions; Checking cooling output (vehicle-specific Workshop

Manual).

♦ Under unfavourable conditions (very high ambient tempera‐

tures, high humidity), the pressure on the high-pressure side

may increase to max. 29 bar.

♦ The specified speed of the air conditioner compressor is dis‐

played as a measured value e.g. by thermal management

control unit - J1024- ⇒ Vehicle diagnostic tester in “Guided

Fault Finding” mode.

♦ The pressure (low or high pressure) in the refrigerant circuit,

as measured by the various pressure/temperature senders

depending on the corresponding operating mode, is displayed

as a measured value by the corresponding control unit ⇒ Ve‐

hicle diagnostic tester in “Guided Fault Finding” mode and ⇒

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

hicle-specific Workshop Manual).

♦ Depending on the air conditioner compressor speed and the

characteristic curve of the expansion valve (on the evaporator

for the front heater and air conditioning unit), the low pressure

settles within the air conditioner compressor output range in

the tolerance band (1.5 to 2.3 bar).

♦ The specified air conditioner compressor speed must be high‐

er than 1500 rpm for this test.

♦ In the “maximum cooling output” setting, the specified speed

is regulated to approx. 4000 to 5000 rpm. This value is vehicle-

specific and is displayed as a measured value by the corre‐

sponding control unit ⇒ Vehicle diagnostic tester in “Guided

Fault Finding” mode.

256

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

♦ On the absolute pressure scale, 0 bar corresponds to an ab‐

solute vacuum. Normal ambient pressure corresponds to an

absolute pressure of 1 bar. On the scales of most pressure

gauges, 0 bar corresponds to an absolute pressure of one bar

(can be seen from -1 mark below 0).

♦ On vehicles with 2 evaporators (one in the heater and air con‐

ditioning unit and one for cooling the high-voltage compo‐

nents, e.g. the high-voltage battery heat exchanger) and 2

condensers (one on the front end for the air conditioner and

one as a heat exchanger for the heat pump function): If the

measured temperatures or pressures correspond to the spec‐

ifications for one component but not for another component

(depending on the selected function), check the activation of

the electrically activated valves installed in the refrigerant cir‐

cuit. Also observe the pressure distribution in the refrigerant

circuit (depending on the non-return valves installed) ⇒ Vehi‐

cle diagnostic tester in “Guided Fault Finding” mode and ⇒

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

hicle-specific Workshop Manual).

♦ For correct operation of the air conditioner, it is also necessary

for sufficient heat to be supplied to or discharged from the cor‐

responding heat exchangers (depending on the selected func‐

tion). You should therefore also pay attention to the incorpo‐

ration of the heat exchanger into the corresponding coolant

circuits for the engine and for the high-voltage system, and to

the operation of the pumps and valves installed in these ⇒ Ve‐

hicle diagnostic tester in “Guided Fault Finding” mode and ⇒

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

hicle-specific Workshop Manual).

♦ As the output of the evaporator for cooling the high-voltage

components (in the battery cooling module and in the high-

voltage battery heat exchanger) is less than that of the evap‐

orator in the heater and air conditioning unit, the required

temperature may still be reached in the evaporator for cooling

the high-voltage components when there is insufficient refrig‐

erant in the circuit, but the required temperature will no longer

be reached at the evaporator in the heater and air conditioning

unit (although the air conditioner compressor is being activa‐

ted at a higher speed).

Possible deviation from speci‐

fication

Possible causes of fault

Fault elimination

•

High pressure remains con‐ ♦ Not enough refrigerant in circuit

stant or only increases

– Extract refrigerant from re‐

frigerant circuit.

slightly (above pressure

with engine stopped)

•

If quantity of refrigerant ex‐

tracted is substantially less

than specified capacity:

•

Low pressure drops quickly

to specified value or below.

– Locate leak with leak detec‐

tor and repair it.

Required cooling output is

not attained in evaporator in

air conditioning unit and in

evaporator for cooling high-

voltage components.

– Re-charge refrigerant circuit.

– Repeat test.

•

If amount of refrigerant ex‐

tracted roughly corresponds

to specified capacity:

– Check activation and opera‐

tion of air conditioner com‐

pressor and of valves instal‐

led in refrigerant circuit (see

below).

8. Checking pressures

257

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

Air conditioner with refrigerant R134a - Edition 11.2018

Possible deviation from speci‐

Possible causes of fault

Fault elimination

fication

♦ Activation of air conditioner compres‐ – Check activation and opera‐

sor not OK

tion of air conditioner com‐

pressor ⇒ Vehicle diagnostic

tester in “Guided Fault Find‐

ing” mode

•

High pressure normal

♦ One of the valves installed in the re‐ – Check operation and activa‐

frigerant circuit is defective or does not

function properly ⇒ Heating, air condi‐

tioning; Rep. gr. 87 ; Refrigerant circuit

(vehicle-specific Workshop Manual).

tion of the various valves in‐

stalled in refrigerant circuit

by observing pressure distri‐

bution in refrigerant circuit

⇒ Vehicle diagnostic tester in

“Guided Fault Finding” mode

and ⇒ Heating, air condition‐

ing; Rep. gr. 87 ; Refrigerant

circuit (vehicle-specific

Low pressure corresponds

to specified value

•

Required cooling output is

not attained.

Workshop Manual).

♦ Not enough refrigerant in circuit

– Discharge and refill refriger‐

ant circuit (see above).

♦ Shut-off valve upstream of expansion

valve for evaporator in front heater and

air conditioning unit defective

– Repeat test.

– Check shut-off valve ⇒ Heat‐

ing, air conditioning; Rep. gr.

87 ; Refrigerant circuit (vehi‐

cle-specific Workshop Man‐

ual).

♦ Expansion valve for evaporator in front

heater and air conditioning unit defec‐

tive

– Renew expansion valve.

258

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

♦ To locate the possible cause of a malfunction, various routines

have been stored in the basic setting of the corresponding

control unit (e.g. -J1024- ); these routines activate the “Air

conditioner cooling”, “Heat pump” and “Cooling of high-voltage

system components” functions ⇒ Vehicle diagnostic tester in

“Guided Fault Finding” mode.

♦ If no fault is detected for this issue, first check the activation of

the electrically activated valves installed in the refrigerant cir‐

cuit. If no fault can be detected, remove and check the non-

return valves installed in the refrigerant circuit; if it is still not

possible to detect a fault, clean the refrigerant circuit (with re‐

frigerant R134a); the issue may alternatively have been

caused by a constriction or blockage in the refrigerant circuit

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

(vehicle-specific Workshop Manual) and ⇒ page 100 .