A/C Signal: Testing and Inspection

Signal From/to Air Conditioning System

Special tools and equipment
- VAG1551 scan tool or VAG1552 mobile scan tool with VAG1551/3B cable
- VAG1598/31 test box
- VAG1526 hand multimeter or VAG1715 multimeter
- VAG1594 adapter set
- Wiring diagram

Test conditions
- Air conditioner functioning OK.
- Air conditioner must be switched off
- No codes must be stored in DTC memory, Check DTC Memory. Refer to "Displaying and Reading Trouble Codes/With Manufacture Scan Tool/Check DTC Memory (Function 02)" Testing and Inspection
- Vehicle at room temperature (warmer than +15 °C).

Test sequence
- Connect VAG1551 scan tool (VAG1552). Start engine and select "Address word" 01 of engine control module. Engine must be running at idling speed. (Connecting scan tool and selecting engine control module). Refer to "VAG1551 Scan Tool Tools and Equipment

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 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 measured value block 50 ->
1 2 3 4


- Observe display in display zone 4. It must show
Comper. OFF.
- Switch on air conditioning system.
- Select lowest temperature and highest blower speed.
The display in display zone 4 must change to
Compr. ON.
- Floor accelerator pedal quickly and then release (brief burst of throttle).
The display in display zone 4 must change from
Compr.ON
to
Compr. OFF
for a few seconds (compressor switch-off when vehicle is accelerating).
- 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 VAG1598/31 test box to control module wiring harness. Engine control module remains disconnected.
- Check wiring for open circuit between test box sockets 40 + 41 and air conditioner system using wiring diagram.
Wire resistance: max. 1.5 Ohm

If no fault can be found in the wiring:
- 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 and Reading Trouble Codes/With Manufacture Scan Tool/Check DTC Memory (Function 02)" Testing and Inspection
- Read readiness code. If DTC memory has been erased or engine control module was disconnected from permanent positive, readiness code must be generated again: Refer to "Monitors, Trips and/or Drive Cycle/ Reading Readiness Code" Testing and Inspection
Engine code AWW, Refer to "Monitors, Trips and/or Drive Cycle/Generating Readiness Code" Testing and Inspection
Engine code AWP, Refer to "Monitors, Trips and/or Drive Cycle/Generating Readiness Code" Testing and Inspection