A/C Signal: Testing and Inspection

Air Conditioning Compressor Signal, Checking

Special tools, testers and auxiliary items
- VAG 1551 Scan Tool (ST) or vehicle system tester VAG 1552 with VAG 1551/3 adapter cable
- VAG 1598/18 test box
- Multimeter (Fluke 83 or equivalent)
- VW 1594 connector test kit
- Wiring diagram

Check conditions
- Air conditioning OK
- Air conditioning switched off
- Vehicle interior ambient temperature above 15 °C (59 °F)
- No malfunctions stored in Diagnostic Trouble Code (DTC) memory See "On-Board Diagnostic/Checking Diagnostic Trouble Code Memory (Function 02)". Testing and Inspection

Test sequence
- Connect VAG 1551 scan tool (VAG 1552) and insert "Engine Electronics" address word 01. Carry out selection at idle. See "On-Board Diagnostic/Connecting VAG 1551 Scan Tool and Selecting Function". Testing and Inspection

Indicated on display

Rapid data transfer HELP
Select function XX

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

Indicated on display

Read measuring value block HELP
Input display group number XXX

- Press -0-, -0- and -5- to input display group number 005.
- Press -Q- button to confirm input.

Indicated on display (1, 2, 3 and 4 = Display fields)

Read measuring value block 5 ->
1 2 3 4

- Observe 5-digit block in display field 4.
- 1st and 2nd positions from left must display zero

Display __00

- Switch on air conditioner (lowest temperature and highest blower speed).
- 1st and 2nd positions from left must now display 1

Display __00

If the display is not as described:





- Connect VAG 1598/18 test box to ECM wiring harness.
- Check wiring for open circuit between test box sockets 37/39 and air conditioner, according to wiring diagram.

Wire resistance: Max. 1.5 Ohms