Get Checking pressures -> Checking pressures in refrigerant circuit with air conditioner service station (with ignition switched off) 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

All vehicles

⇒ “8.1 Checking pressures in refrigerant circuit with air conditioner

service station (with ignition switched off)”, page 195

⇒ “8.2 Checking pressures - vehicles with restrictor and reservoir

(with internally regulated air conditioner compressor)”,

page 201

⇒ “8.3 Checking pressures - vehicles with expansion valve and

receiver (with internally regulated air conditioner compressor)”,

page 206

⇒ “8.4 Checking pressures - vehicles with restrictor, reservoir and

air conditioner compressor regulating valve N280 (with externally

regulated air conditioner compressor)”, page 212

⇒ “8.5 Checking pressures - vehicles with expansion valve, re‐

ceiver and air conditioner compressor regulating valve N280 (with

externally regulated air conditioner compressor)”, page 219

⇒ “8.6 Checking pressures - vehicles with electrically driven air

conditioner compressor (vehicles with high-voltage system)”,

page 230

8.1

Checking pressures in refrigerant circuit

with air conditioner service station (with

ignition switched off)

Note

♦ All test requirements marked with an * are vehicle-specific and

are described in the Workshop Manual for the relevant vehicle.

♦ Check cooling output.*

♦ Connections with valve and service connections for measuring

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

erant circuit (vehicle-specific Workshop Manual).

♦ Depending on the version of the air conditioner compressor,

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

pressor which prevents liquid refrigerant from flowing back into

the compressor after the air conditioner has been switched off.

If an air conditioner compressor with such a valve is installed

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

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

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

pressure in the low-pressure side increases rapidly after the

compressor is switched off; the expansion valve is closed and

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

If the air conditioner compressor is switched on, the pressure

in the low-pressure side drops, the expansion valve is opened

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

Under certain operating conditions, residual moisture in the cool‐

ant circuit may lead to the formation of ice at the air conditioner

compressor regulating valve. Such ice formation impedes the

control of the air conditioner compressor. The evaporator is

cooled down too much and ices up. An iced-up evaporator may

cause the following problems:

♦ The air conditioning system fails repeatedly or sporadically (no

cooling/heating output) after extended driving; after the vehicle

has been stopped, the air conditioner functions properly again

(after a short wait).

♦ Misting up of the windows (front windscreen, side windows

and / or rear windscreen) on the inside after a long journey;

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

8. Checking pressures

195

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

Air conditioner with refrigerant R134a - Edition 11.2018

frost button; the air conditioner functions properly again after

a short delay following engine shut-off.

Remedy:

– In the case of vehicles as of Model Year 2001 and an air con‐

ditioner compressor with air conditioner compressor regulat‐

ing valve - N280- , check the measured value of the evaporator

output temperature sender - G263- (by way of the “Reading

measured value block” function). If the measured value of the

sender is too low under the usage conditions outlined by the

customer (at ambient temperatures above 0 °C, below 0 °C for

a lengthy period although -N280- is not being activated) or too

high (above approx. 10 °C although air conditioner is operating

properly), The evaporator may ice up due to the incorrect

measured value ⇒ Vehicle diagnostic tester (“self-diagnosis”

or “Guided Fault Finding” function for air conditioner) and ⇒

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

hicle-specific Workshop Manual).

– On vehicles without an evaporator output temperature sender

- G263- , use for example footwell vent temperature sender -

G192- to check vent temperature under operating conditions

described by customer in the following settings: "Lo tempera‐

ture" for driver and passenger side, 4 or 5 bars for fresh air

blower speed, air outlet to footwell and fresh-air mode. If

measured value of sender is too low (at ambient temperature

above 0°C, colder than 0°C for lengthy period).

– Check refrigerant line between evaporator and reservoir (thick

line, low-pressure side) with engine running. If this line is se‐

verely iced up when the problem occurs (thin layer of ice is

permissible), this also indicates that evaporator temperature

is too low.

– Discharge refrigerant circuit, renew reservoir or receiver with

dryer and then evacuate refrigerant circuit for at least 3 hours.

⇒ “8.1.1 Test requirements”, page 196

⇒ “8.1.2 Checking pressures ”, page 198

8.1.1

Test requirements

Note

This section describes the test requirements for a vehicle with a

mechanically driven air conditioner compressor as an example.

These requirements differ on vehicles with high-voltage system

(e.g. Audi A3 e-tron, Audi Q7 e-tron) or with additional air condi‐

tioner functions (e.g. Audi Q7 e-tron). On these vehicles, note the

corresponding information in the Workshop Manual and in Guided

Fault Finding ⇒ Heating, air conditioning; Rep. gr. 00 ; Repair

instructions; Checking cooling output (vehicle-specific Workshop

Manual) and ⇒ Vehicle diagnostic tester in “Guided Fault Finding”

mode.

•

Radiator and condenser clean (clean if necessary)

Thermal insulation at expansion valve OK and properly instal‐

led*

•

Poly V-belt OK and properly tensioned. / belts for air condi‐

tioner compressor and alternator OK and properly tensioned.*

•

All air ducts, covers and seals OK and properly installed

No faults detected during fault-finding on electrical system and

vacuum system* ⇒ Vehicle diagnostic tester (“self-diagnosis”

or “Guided Fault Finding” function for air conditioner) and ⇒

196

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

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

hicle-specific Workshop Manual).

•

No fault detected during air conditioner self-diagnosis (with

engine running and air conditioning system switched on), no

compressor shutoff criteria displayed in measured value block

(vehicles with “air conditioning system” self-diagnosis only).*

⇒ Vehicle diagnostic tester (“self-diagnosis” or “Guided Fault

Finding” function for air conditioner) and ⇒ Heating, air con‐

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

Workshop Manual).

Check whether the various pressure/temperature senders and

temperature sensors installed in the refrigerant circuit deliver

plausible measured values during operation of the air condi‐

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

⇒ Heating, air conditioning; Rep. gr. 87 ; Overview of fitting

locations - air conditioner . If no fault is found, extract refriger‐

ant.

•

Air flow through dust and pollen filter not impeded by dirt*

Air conditioning unit not drawing in secondary air at maximum

fresh air blower speed; evaporator and heater not drawing in

secondary air at maximum fresh air blower speed*

•

Air flaps in air conditioning unit, heater and evaporator reach

end position*

Fresh-air intake ducts beneath bonnet and in passenger com‐

partment as well as corresponding water drain valves OK* ⇒

Heating, air conditioning; Rep. gr. 87 ; Air ducting (vehicle-

specific Workshop Manual).

•

Engine at operating temperature

Vehicle not exposed to sunlight ⇒ Heating, air conditioning;

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

(vehicle-specific Workshop Manual)

•

Ambient temperature above 15 °C

All dash panel vents open

– Start engine.

Setting on the air conditioning system control unit, e.g. on the op‐

erating and display unit for front air conditioning system - E87- or

the Climatronic control unit - J255- (and the rear Climatronic op‐

erating and display unit - E265- on vehicles with two air condi‐

tioning units):

– Select “Auto” mode (air conditioner compressor switched on).

– Set “LO” temperature for driver and front passenger side (and

rear left and right of passenger compartment in vehicles with

two air conditioning units).

Settings on heater controls:

– Press A/C button and "Rec" or recirculated air button.

– Turn the rotary temperature control towards the “cold” stop.

– Set rotary fresh air blower control to “4”.

Subsequently, the following system test requirements should be

met:

•

Radiator fan - V7- (and radiator fan 2 - V177- if fitted) must be

running (at least at speed 1).*

8. Checking pressures

197

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

Air conditioner with refrigerant R134a - Edition 11.2018

Note

With some versions, the fan is not switched on until the pressure

in the refrigerant circuit has exceeded a specified value.

•

Fresh air blower - V2- (and rear fresh air blower - V80- on

vehicles with two air conditioning units) run(s) at maximum

speed.

•

Air recirculation flap/fresh air flap is in “Air recirculation mode”

position (air flow flap is closed and air recirculation flap opened

within 1 min. after the vehicle is started).*

•

Coolant shut-off valve closed.*

Valves of pump valve unit closed and no coolant circulation

pump delivery*

•

Air conditioner compressor is actually driven ( air conditioning

system magnetic clutch - N25- energised, overload protection

(if fitted) not tripped).*

Note

Depending on the engine, the air conditioner compressor is driven

by different components (belt or drive shaft). To protect these

components and the engine, the pulley or the drive unit of the air

conditioner compressor are fitted with an overload protection de‐

vice, which is triggered if the air conditioner compressor is not

operating smoothly ⇒ Heating, air conditioning; Rep. gr. 87 ; Air

conditioner compressor (vehicle-specific Workshop Manual).

8.1.2

Checking pressures

♦ Observe test requirements ⇒ page 196 .

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

auxiliary air conditioner function ⇒ Owner's Manual and ⇒

Infotainment/MMI Operating Manual .

– Switch off ignition.

– Connect air conditioner service station ⇒ page 187 .

Vehicles with electrically operated valves in the refrigerant circuit

which are not open when the system is de-energised (e.g. on the

Audi Q7 e-tron):

Note

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

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

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

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

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

after the ignition is switched off. However, for the pressure in the

refrigerant circuit to be checked when the air conditioner is switch‐

ed off, no part of the circuit may be closed off; these valves must

therefore be opened before performing such work ⇒ Heating, air

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

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

Finding”).

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

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

198

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

energised ⇒ Vehicle diagnostic tester (“Guided Fault Find‐

ing”).

All vehicles

– Read pressures off pressure gauges; there are two possible

results:

♦ The pressure in the refrigerant circuit is lower than indicated

in the table.

♦ The pressure in the refrigerant circuit corresponds to that in‐

dicated in the table or is higher.

Ambient temperature (in de‐ Pressure in refrigerant circuit in

grees centigrade)

+15 °C

bar

3.9

4.7

5.6

6.7

7.8

9.1

10.5

+20 °C

+25 °C

+30 °C

+35 °C

+40 °C

+45 °C

Note

♦ The temperature of the refrigerant circuit components should

be equal to the ambient temperature. (the pressure will deviate

from the values in the table if individual components of the

refrigerant circuit are warmer or colder).

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

solute vacuum. The normal ambient pressure (atmospheric

pressure) corresponds to 1 bar absolute pressure. On the

scales of most pressure gauges, 0 bar corresponds to an ab‐

solute pressure of 1 bar (can be seen from -1 bar mark below

0).

♦ On vehicles with a high-pressure sender - G65- , pressure

sender for refrigerant circuit - G805- or refrigerant pressure

and temperature sender - G395- etc. for which the measured

pressure is displayed in the measured value block, the pres‐

sure measured should coincide with the values in the table ⇒

Vehicle diagnostic tester (“Self-diagnosis” or “Guided Fault

Finding” function for air conditioner) and ⇒ Heating, air con‐

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

Workshop Manual).

♦ Pressure can be measured in various units: 1 MPa (mega‐

pascal) is equivalent to 10 bar gauge pressure, or 145 psi; 1

bar absolute pressure is the same as 0 bar gauge pressure,

which is roughly equivalent to atmospheric pressure.

The pressure in the refrigerant circuit is lower than indicated in

the table.

Not enough refrigerant in circuit

– Locate leaks in refrigerant circuit ⇒ page 169 .

– Check high-pressure safety valve.

If the high-pressure safety valve has blown off:

– Check actuation of the radiator fans.

– Check for constricted refrigerant pipe and hose cross-sections

caused by inadequate bending radii.

8. Checking pressures

199

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

Air conditioner with refrigerant R134a - Edition 11.2018

– Check refrigerant lines and hoses for external damage.

– If no fault is found, clean refrigerant circuit (by flushing with

refrigerant R134a ⇒ page 100 or blowing out with compressed

air and nitrogen ⇒ page 95 ).

The pressure in the refrigerant circuit corresponds to that indica‐

ted in the table or is higher.

– Start engine or activate drive system (e.g. on vehicles with

high-voltage system).

– Set air conditioning system to maximum cooling output.

Note

♦ On vehicles with an air conditioner compressor regulating

valve - N280- , the control current can be read out in the meas‐

ured value block ⇒ Vehicle diagnostic tester (“Self-diagnosis”

or “Guided Fault Finding” function for air conditioner) and ⇒

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

pressor (vehicle-specific Workshop Manual).

♦ On vehicles with an electrical air conditioner compressor -

V470- you can read out the air conditioner compressor speed

via different control units (e.g. via the corresponding air con‐

ditioner control unit or the thermal management control unit -

J1024- ) ⇒ Vehicle diagnostic tester in “Guided Fault Finding”

mode.

Vehicles with a mechanically driven air conditioner compressor

If air conditioner compressor is not driven with engine running or

regulating valve is not actuated:

– Establish and eliminate the cause e.g. by interrogating the air

conditioner event memory.

– Observe test requirements.

– Check the power supply for the air conditioning system mag‐

netic clutch - N25- . If this is OK, service the magnetic clutch.

– Check activation of air conditioner compressor regulating

valve - N280- ⇒ Vehicle diagnostic tester (“Self-diagnosis” or

“Guided Fault Finding” function for air conditioner) and ⇒

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

pressor (vehicle-specific Workshop Manual).

Note

♦ If low-pressure switch has been removed to connect air con‐

ditioner service station, jumper electrical connections in rele‐

vant connector for pressure measurement.

♦ Air conditioner compressor is driven by engine via air condi‐

tioning system magnetic clutch - N25- .

♦ The air conditioner compressor regulating valve - N280- is ac‐

tivated by the operating and display unit for front air condition‐

ing system - E87- or the Climatronic control unit - J255- ⇒

Vehicle diagnostic tester (“Self-diagnosis” or “Guided Fault

Finding” function for air conditioner) and ⇒ Heating, air con‐

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

Workshop Manual).

200

Rep. gr.87 - Air conditioning system

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