A/C Signal: Testing and Inspection

Signal from/to A/C compressor, checking

Special tools and equipment
- VAG1551 Scan Tool (ST) or VAG1552 mobile scan tool with VAG1551/3 adapter cable
- VAG1598/22 test box
- Multimeter (Fluke 83 or equivalent)
- VW1594 adapter set
- Wiring diagram

Test conditions
- Air conditioner functioning OK
- Air conditioner switched off
- No DTCs stored in DTC memory.
- All electrical consumers (e.g. lights and window defroster) switched off
- Battery (B+) voltage at least 11.5 V
- Vehicle at room temperature (warmer than + 15°C).

Test sequence
- Connect VAG1551
- Switch ignition on and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (when doing this engine must be running at idle).

Indicated on display

Rapid data transfer HELP
Select function XX

- Press buttons -0- and -8- to select "Read Measuring Value Block" function 08 and press -Q- button to confirm input.

Indicated on display

Read Measuring Value Block
Input display group number XXX

- Press buttons -0-, -5- and -0- to input display group number 50 (050) and press -Q- button to confirm input.

Indicated on display: 11-4 = display fields)

Read Measuring Value Block 50 ->
1 2 3 4

- Check specified values for air conditioner (display fields 3 and 4).






- Observe display in display field 4.
It must show Compr. OFF.
- Switch air conditioning system on.
- Select lowest temperature and highest blower speed.
The display in display field 4 must change to Compr. ON.
- Press -> button.

- Press buttons -0- and -6- to select "End Output" function 06 and press -Q- button to confirm input.
- Switch ignition off.

Continuation

If the display does not change:
- Remove wiper arms and plenum chamber cover.






- Connect VAG1598/22 test box to control module wiring harness.
- Check wiring between test box sockets 8 + 10 and air conditioner for open circuit according to wiring diagram.

- Wire resistance: max. 1.5 ohms

If no malfunction can be found in the wiring:
- Check function of air conditioner control module.
- Check DTC memory. If necessary, repair any malfunctions and erase DTC memory.

- Display readiness code.
If DTC memory has been erased or the Engine Control Module (ECM) was disconnected from permanent battery (B+) voltage, the readiness code must be generated again.