Checking the air conditioner compressor shutoff — AUDI

Special tools and workshop equipment required

V.A.G 1526 A
V.A.G 1594 A
V.A.G 1598 A
V.A.G 1598/11
VAS 5051 with VAS 5051/1 and VAS 5051/2

or

V.A.G 1551 with V.A.G 1551/1

Note:

Air conditioner compressor is switched off by engine control unit on accelerating and by gearbox control unit at full throttle (kickdown switch). Compressor shutoff is bidirectional:
In: Voltage is applied to control unit shortly before switching on air conditioner compressor. The control unit then causes the idling stabilistion valve to open slightly more to compensate for the higher load.
Out: The air conditioner compressor is shut off by the engine control unit on accelerating from standstill and from low vehicle speed for approx. 12 seconds. If the accelerator pedal is released sooner, the time is reduced to min. 3 seconds.
The air conditioner compressor is also shut off by the engine control unit after initiating function 04 "Basic setting".

Test requirements:

No faults stored in fault memory
Engine running at idling speed
Vehicle at ambient temperature (warmer than + 15 oC).
Air conditioning system OK

Test sequence

Switch on air conditioner as follows:
Manual air conditioner: Press the "AC" key.
Fully automatic air conditioner: Press the "AUTO" key, set temperature to "LO" and fan speed to "HI".

Start basic setting =>Page
01-82
, Display group 004, engine idling.

Basic setting 4
⇒ (1) (2) (3) (4)
Indicated on display:

Air-conditioner compressor must come to a halt (visual inspection)

If the conditioner compressor is not switched off:

Switch off air conditioner and leave engine idling.
Enter "8" for switching to "Reading measured value block" function.

Read measurement block 4
⇒ (1) (2) (3) (4)
Indicated on display:

Specified value in display zone 4 for control unit no. 8A0 906 266 Index "C": X0X X
Specified value in display zone 4 as of control unit no. 8A0 906 266 E: X0X XX

Note:

Switching inputs at locations marked "X" can be ignored for this test.

Switch on air conditioner =>Page
24-122.

Read measurement block 4
⇒ (1) (2) (3) (4)
Indicated on display:

Specified value in display zone 4 for control unit no. 8A0 906 266 Index "C": X1X X
Specified value in display zone 4 as of control unit no. 8A0 906 266 E: X1X XX

If the display is not as described:

With the ignition switched off, use adapter V.A.G 1598/11 to connect test box V.A.G 1598 A to engine control unit connector C only (control unit remains disconnected) => Page
24-15.
Check for open circuit and short to positive or earth in the following wiring connections:

Test box / V.A.G 1598 A / socket · Magnetic clutch control unit / -J153 / contact · Operating and display unit / -E87 / contact
10 · => "Current Flow Diagrams, Electrical Fault Finding and Fitting Locations" binder

If there are no faults in the wiring, check the operation of air conditioning.

=> Heating, Air Conditioning; Repair group 87; Air Conditioner, Repair components for manual air conditioning
Heating, Air Conditioning
Air Conditioner, Repair components for manual air conditioning

=> Heating, Air Conditioning; Repair group 87; Air Conditioner, Repair control components for fully automatic air conditioning
Heating, Air Conditioning
Air Conditioner, Repair control components for fully automatic air conditioning

If both air conditioner and wiring OK:

Replacing engine control unit => Page
24-18.