Testing cooling capacity of air conditioner — AUDI

Special tools, testers and other items required

Fault reader V.A.G 1551 (or vehicle system tester V.A.G 1552) with wire V.A.G 1551/3
Minitester V.A.G 1362

Test requirements:

Radiator and condenser clean (clean if necessary).
Ribbed belt for compressor drive OK and properly tensioned.
All air ducts, covers and seals OK and properly fitted.
Air flow through dust and pollen filter not impaired by dirt.
Vehicle not exposed to sunlight.
Engine warm.
Code checked and, if necessary, corrected => Page
01-106
.
Basic setting performed => Page
01-101
.

Fault memory interrogated => Page
01-104
.
Settings on operating and display unit -E87:
"Auto" mode for driver's and front passenger's side.
Temperature preset to "LO" for driver's and front passenger's side.
"ECON" button not switched on (compressor ON).

Functions with engine running:
Compressor is driven (magnetic coupling is switched on).
Radiator fan -V7 is running (at least at speed 1).
Fresh air blower -V2 is running at maximum speed.
Air flow flap closes and air recirculation flap opens (approx. 1 minute after vehicle is started).
Coolant circulation pump -V50 is not running.

Heat regulation valves -N175 and -N176 are closed (coolant hoses and pipes to heating system heat exchangers cool down).

Notes:

If one of these test requirements is not met, interrogate the fault memory => Page
01-70
.
Test heating capacity of air conditioner and check functioning of pump/valve unit =>Page
87-164
.

Testing

A -
Air temperature from "centre" dash panel vents
B -
Ambient temperature
C -
Permissible tolerance range

Depending on the ambient temperature, the temperature of the air from the "centre" dash panel vents must be within the specified tolerance range after 5 minutes.

Close bonnet.
Measure ambient temperature.
Close doors, windows and sun roof.

Close "right" and "left" dash panel vents.
Close B-pillar vents.
Switch on ignition.
Open "centre" dash panel vents.
Set handwheel for temperature-adjustable centre vent to "warm".
Set "Auto" mode for driver's and front passenger's side.
Preset temperature to "LO" for driver's and front passenger's side.
Start engine (start of time measurement).
Set engine speed to 2000 rpm.

Measure temperature of air flowing out of "centre" dash panel vents, e.g. using minitester V.A.G 1362.
Compare measured values to values in graph.

Notes:

If the required values are not attained => Page
87-159
(Measures to be taken if actual value deviates from specified value).
It is advisable to use two separate thermometers for this measurement.
The temperature of the air in the mixing boxes of the air conditioner unit (downstream of the heat exchanger) can be measured in the measured value block using the V.A.G 1551 while the cooling capacity is being tested =>Display group 014, Page
01-158
.
If the air conditioner is functioning correctly, the coolant pipe on the low-pressure side (thick pipe) will cool down.
If cooled air is discharged from the temperature-adjustable centre vent when set to "cold" and non-cooled air when set to "warm", check the heat regulation valves -N175 and -N176.
If the cooling capacity on the front passenger's side is still adequate but the specified values for the driver's side are no longer attained, this is an indication that there is a coolant leak (layers in evaporator).

Measures to be taken if actual value deviates from specified value

▪ Compressor shut off during cooling capacity test?
↓ / yes / ↓ · ↓ / no / ↓
- Continue test =>Page . 87-161 · - Clamp off both coolant hoses from engine to pump/valve unit using hose clamps 3093/3094. / ↓
- Repeat cooling capacity test =>Page . 87-154 / ↓
▪ Is required cooling capacity attained?
↓ / yes / ↓ · ↓ / no / ↓
- Detach hose clamps 3093/3094 from both coolant hoses. / ↓ · - Vehicle must be taken to specialist VW/Audi air conditioner workshop (fault in refrigerant circuit).
- Check actuation of heat regulation valves -N175, -N176 and coolant circulation pump -V50 => Page . 87-164
↓ / Continued t

▪ Is actuation of heat regulation valves and coolant circulation pump OK?
↓ / yes / ↓ · ↓ / no / ↓
- Connect test box V.A.G 1598/19 to wiring harness of operating and display unit -E87 =>Page . 01-183 / ↓ · - Eliminate cause of fault =>Electrical testing,Page and 01-196
- Perform electrical test on valves -N175, -N176 and pump -V50 =>Page . 01-196 / ↓ · => Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder / ↓
▪ Are valves -N175, -N176 and pump -V50 functioning OK? · ↓
↓ / yes · ↓ / no · - Repeat cooling capacity test =>Page . 87-154
↓ / Replace operating and display unit -E87 =>Page . 87-96 / ↓ · ↓ / Replace pump/valve unit =>Page . 87-71 / ↓
- Repeat cooling capacity test =>Page . 87-154

Continuation of test - Compressor was switched off during cooling capacity test
- Interrogate fault memory => Page . 01-125 / Repeat cooling capacity test and observe display zone 1 on display of V.A.G. 1551
▪ Is required cooling capacity attained (compressor was not switched off)?
↓ / yes / ↓ · ↓ / no / ↓
End · ▪ Is following code displayed as compressor shut-off condition in display zone 1?
↓ / Code 1 / ↓ · ↓ / Code 3 / ↓ · ↓ / Other code / ↓
▪ High-pressure switch -F118/-F23 and/or high-pressure switch in pressure switch -F129 open / Continue test =>Page . 87-162 · ▪ Low-pressure switch -F73 open / Continue test =>Page . 87-163 · - Further codes =>from Page onwards 01-125

Continuation of test - Compressor shut-off condition Code "1"
▪ Was radiator fan -V7 switched to speed 2 during test?
↓ / yes / ↓ · ↓ / no / ↓
- Replace high-pressure switch -F118/-F23 and/or pressure switch -F129. / Repeat cooling capacity test. / ↓ · - Unplug connector of high-pressure switch -F118/-F23 and jumper contacts "1" and "2" => Page . 87-17 / ↓
▪ Is required cooling capacity attained (compressor was not switched off)? · ▪ Is radiator fan running at speed 2?:
↓ / yes / ↓ · ↓ / no / ↓ · ↓ / yes / ↓ · ↓ / no / ↓
End · - Reinstall old switch / -F118/-F23 and/or -F129. · - Replace high-pressure switch -F118/-F23. · - Use current flow diagram to service actuation of radiator fan -V7.
- Vehicle must be taken to specialist VW/Audi air conditioner workshop (fault in refrigerant circuit).

Continuation of test - Compressor shut-off condition Code "3"
- Unplug connector of low-pressure switch -F73 and jumper contacts => Page . 87-154 / ▪ Is required cooling capacity attained?
↓ / yes / ↓ · ↓ / no / ↓
- Replace switch -F73. · ▪ Was compressor switched off again?
- Repeat cooling capacity test. · ↓ · ↓
↓ / ▪ Is required cooling capacity attained? · yes / ↓ · no / ↓
↓ / ↓ / yes / ↓ · ↓ / ↓ / no / ↓ · - Check wiring to operating and display unit -E87 via switch -F73. · - Vehicle must be taken to specialist VW/Audi air conditioner workshop (fault in refrigerant circuit).
End · - Reinstall old switch -F73. / Vehicle must be taken to specialist VW/Audi air conditioner workshop (fault in refrigerant circuit). · ↓ / Repeat cooling capacity test.