A/C Signal: Testing and Inspection

Signal From/To Air Conditioning, Checking

Special tools, test equipment and auxiliary items
- Scan tool V.A.G 1551 or vehicle system tester V.A.G 1552 with cable V.A.G 1551/3B
- Test box V.A.G 1598/31
- Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
- Adapter set V.A.G 1594
- Wiring diagram

Test Conditions






- Fuses 5, 10 and 29 must be OK
- The battery voltage must be at least 11.5 V
- All electrical consumers, e.g. lights and rear window heating must be switched off
- No DTCs must be stored in DTC memory, checking and erasing DTC memory. Refer to "Displaying, Reading and Erasing Trouble Codes/With Manufacturers Scan Tool/DTC Memory, Checking And Erasing", Testing and Inspection
- Air conditioner functioning OK
- Air conditioner must be switched off
- Vehicle at room temperature (warmer than +15°C)

Test sequence
- Connect scan tool V.A.G 1551 (V.A.G 1552). Start engine and select "Address word" 01 of engine control module. When doing this the engine must be running at idle speed. Connecting scan tool and selecting Engine Control Module (ECM). Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/VAG 1551 Scan Tool", Testing and Inspection

Indicated on display

Rapid data transfer HELP
Select function XX

- Press keys 0 and 8 for the function "Read measuring value block" and confirm entry with Q key.

Indicated on display

Read measuring value block
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 (1-4 = Display zones)

Read measuring value block 50 ->
1 2 3 4

- Check specifications for air conditioner (display zones 3 and 4)

Display Group 50:

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

- Press the -> key.
- Press keys 0 and 6 for the "End output" function and confirm input with the Q key.
- Switch off ignition.

Continuation

If the display does not change:
- Remove inner plenum chamber cover at left:






- Connect test box V.A.G 1598/31 to control module wiring harness. The engine control module is not connected by this action.
- Check wiring for open circuit between test box sockets 40 + 41 and air conditioner system using wiring diagram.
Wire resistance: max. 1.5 Ohms

If no wiring malfunctions can be found:
- Check function of air conditioner control module.
- Check DTC memory, if necessary, repair any malfunctions and then erase DTC memory, checking and erasing DTC memory. Refer to "Displaying, Reading and Erasing Trouble Codes/With Manufacturers Scan Tool/DTC Memory, Checking And Erasing", Testing and Inspection
- Read-out the readiness code. If the DTC memory has been erased or the engine control module was disconnected from permanent positive, the readiness code must be generated again.
Refer to "Monitors Trips and/or Drive Cycle/Displaying Readiness Code", Testing and Inspection
Refer to "Monitors Trips and/or Drive Cycle/Generating Readiness Code", Testing and Inspection