Checking signal from/to air conditioner — VW

Special tools, workshop equipment, testers, measuring instruments and auxiliary items required

Fault reader V.A.G 1551 or vehicle system tester V.A.G 1552 with cable V.A.G 1551/3
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
Current flow diagram

Test conditions

Fuses 5, 10 and 29 must be OK.
Air conditioner functioning OK.
Air conditioner must be switched off
No faults must be stored in fault memory:

Interrogate fault memory, if necessary, repair any faults and then erase fault memory => Page
01-18
, interrogating and erasing fault memory.

All electrical consumers, e.g. lights and rear window heating must be switched off
The battery voltage must be at least 11.5 V.
Vehicle at room temperature (warmer than + 15 °C).

Test sequence

Connect fault reader V.A.G 1551 (V.A.G 1552). Start engine and select "Address word" 01 of engine control unit. When doing this the engine must be running at idling speed.
(Connecting fault reader and selecting engine control unit => Page
01-9
.)

Rapid data transfer
HELP
Select function XXX
Indicated on display:

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

Read measured value block
Input display group number XXX
Indicated on display:

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

Read measured value block 50
⇒
1
2
3
4
Indicated on display:
(1...4 = Display zones)

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

Display zones
1 · 2 · 3 · 4
Display group 50: Signals to engine control unit
Display · xxxx rpm · xxxx rpm · A/C-LOW / A/C-High · Compr. OFF / Compr. ON
Indicated · Actual engine speed / (in steps of 10) · Specified engine speed / (in steps of 10) · Air conditioner status · Air conditioner compressor status
Working range · --- · --- · --- · ---
Specification · 640...1240 rpm · 700...1200 rpm · Air cond. system off: / A/C-Low / Air cond. system on: / A/C-High · Air cond. system off: / Compr. OFF / Air cond. system on: / Compr. ON
--- · --- · If the specifications are not achieved / => Page , Continuation 24-187

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 3 must change to
A/C-High.

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

The following description deals with the Golf 1998 ä, Bora 1999 ä. Therefore differences must be considered, if necessary.

If the display does not change:

Remove wiper arms and cowl panel:

=> Electrical system; Repair group 92; windscreen wiper system; removing and installing windscreen wiper system
Electrical system
windscreen wiper system
removing and installing windscreen wiper system

Connect test box V.A.G 1598/31 to control unit wiring harness. The engine control unit remains disconnected.
Check wiring for open circuit between test box sockets 40 + 41 and air conditioner system using current flow diagram.
Wire resistance: max. 1.5 ω

If no fault can be found in the wiring:

Check function of air conditioner control unit.