A/C Signal: Testing and Inspection
Air conditioner compressor shut-off, checking
NOTE:
- The air conditioning compressor signal informs the engine control module that the compressor will be switched on in 140 ms.
- The engine control module can send a signal via the same wire to shut off the air conditioner compressor.
Switching off of the air conditioner compressor occurs:
- In the emergency program (Emergency running mode)
- After initiating of basic setting (Function 04)
- From the transmission control module (Kick down function).
Test conditions
- Air conditioner functioning properly.
- No DTCs recorded in DTC memory of engine control module
- Interior temperature of more than +15 degree C
- Connect vehicle diagnostic, testing and information system VAS 5051 or V.A.G 1551 Scan Tool and select engine electronics control module with "Address word" 01. For this purpose, engine must be running at idle speed.
Indicated on display
Rapid data transfer HELP
Select function XX
- Press keys 0 and 8 for function "Read measured value block" and confirm entry with Q key.
Indicated on display
Read measured value block 08
Enter display group number XXX
- Press keys 0, 5 and 0 for "display group number 50" and confirm entry with Q key.
Indicated on display
Read measured value block 50 ->
1 2 3 4
- Check compressor shut-off in display zone 4.
Display Group 50:
- Switch on air conditioner by pressing "Auto" key.
Compressor should run (display zone 4).
- Set air conditioner to maximum cooling or heating output (display zone 3).
Display Group 50:
- Switch off air conditioning compressor at A/C control head by pressing ECON button.
Specification for display zone 4: Display should change from "Compr. ON" to "Compr. OFF" (compressor switch-off)
If the readout in display zone 4 is not as described:
- Switch ignition off.
- Connect test box VAG 1598/31 to wiring harness for engine control module; do not connect engine control module. Connecting VAG 1598/31 Test Box
- Check following wiring connections for short circuit to positive or Ground or open circuit.
Test box VAG
1598/31 Socket A/C Control head -E87- Contact
41
Wire resistance: max. 1.5 Ohm
- Correct any open/short circuit as necessary.
- If there are no wiring malfunctions, check operation of air conditioning.
- Read readiness code. Generate readiness code again if DTC memory was erased. Readiness Code, Generating