A/C Signal: Testing and Inspection

Signal From/to Air Conditioning System, Checking

Special tools and equipment
- Scan tool VAG 1551 or VAG 1552 with cable VAG 1551/3
- Test box VAG 1598/22
- Hand multimeter VAG 1526 or multimeter VAG 1715
- Adapter set VAG 1594
- Wiring diagram

Test conditions
- Air conditioner functioning OK.
- Air conditioner must be switched off
- No DTCs must be stored in DTC memory, checking DTC memory
- Vehicle at room temperature (warmer than + 15 degree C).

Test sequence
- Connect VAG 1551 Scan Tool ((VAG 1552). Start engine and select "Address word" 01 of engine control module. When doing this 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 Measuring Value Block" and confirm entry with Q key.

Indicated on display

Read Measuring Value Block HELP
Input display group number XXX

- Press keys 0, 5 and 0 for "Display group number 50" and confirm entry with Q key.

Indicated on display: (1 to 4 = Display zones)

Read Measuring Value Block 50 ->
1 2 3 4

- Observe display in display zone 4. It must show Compr. OFF.
- Switch on air conditioning system.
- Select lowest temperature and highest blower speed.
- Display in display zone 4 must change to: Compr. ON.
- Press -> key.
- Press keys 0 and 6 for "End Output" function and confirm input with Q key.
- Switch ignition off.

If the display does not change:







- Connect test box VAG 1598/22 to control module wiring harness.
- Check wiring between test box sockets 8 + 10 and air conditioner for open circuit using wiring diagram.

Wire resistance: Max. 1.5 Ohm