Checking signal from/to air conditioning system: Audi 1.6 (BAH)

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 1598/22
Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
Adapter set V.A.G 1594
Current flow diagram

Test conditions

All electrical consumers, e.g. lights and rear window heating must be switched off.
Air conditioner functioning OK.
Air conditioner must be switched off
Vehicle at room temperature (warmer than + 15 °C).
No faults must be stored in fault memory => Page
01-16
, interrogating and erasing fault memory.

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
01-7
.)

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)

Observe display in display zone 3. It must show
A/C-Low.
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.

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

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 1598/22 to control unit wiring harness
=> Page
24-121
.
Check wiring for open circuit between test box sockets 17 + 42 and air conditioner using current flow diagram.
Wire resistance: max. 1.5 ω

If no fault can be found in the wiring:

Interrogate fault memory, if necessary, repair any faults and then erase fault memory => Page
01-16
, interrogating and erasing fault memory.
Check function of air conditioner control unit.