Testing air conditioner compressor signal and air conditioner compressor shut-off — AUDI

ACZ
Special tools and workshop equipment required

V.A.G 1526 A
V.A.G 1527 B
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

Testing signal from air conditioner compressor

Note:

In vehicles ▸ 05.94 the pre-control value for idling speed stabilisation is increased by the signal from the air conditioner so that the idling speed stabilisation remains in the middle of the control range.

Read measured value block, Display Group 006, engine at idling speed =>Page
01-77
.

Read measured value block 6
⇒
1
2
3
4
Indicated on display:

Check display in display zone 3.
Switch on air conditioner system:
Manually controlled air conditioners: Press the "A/C" button.
Fully automatic air conditioners: Press the "AUTO" button, set the temperature to "LO" and the blower speed to "HI".

Value must increase by at least 16.

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 connector B and additionally to the engine control unit => Page
24-10
.
Connect voltage tester V.A.G 1527 B as follows:

Test box V.A.G 1598 A / socket · Measure to
31 · Engine earth

Switch the ignition on.
Switch on air conditioner system:
Manually controlled air conditioners: Press the "A/C" button.
Fully automatic air conditioners: Press the "AUTO" button, set the temperature to "LO" and the blower speed to "HI".

The LED should light up.

If the LED does not light up:

Disconnect V.A.G 1598/11 adapter from engine control unit connection B.

If the LED then lights up:

Replace engine control unit => Page
24-13
.

If LED still does not light:

Check for open circuit and short to positive or earth in the following wiring connections:

Test box / V.A.G 1598 A / socket · Switch forair conditioner - E30 / / contact · Operating and / display unit / -E87 / contact
31 · => "Current Flow Diagrams, Electrical Fault Finding and Fitting Locations" binder

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

=> Heater, Air conditioner; Repair group 87; Air conditioner; Servicing components of the manually controlled air conditioner
Heater, Air conditioner
Air conditioner
Servicing components of the manually controlled air conditioner

=> Heater, Air conditioner; Repair group 87; Air conditioner; Servicing components for controlling and regulating the fully automatic air conditioner
Heater, Air conditioner
Air conditioner
Servicing components for controlling and regulating the fully automatic air conditioner

Checking the air conditioner compressor shutoff

Note:

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.

Test requirements:

Vehicle at ambient temperature (warmer than + 15 oC)
Vehicles with automatic gearbox: Selector lever in position P or N
No faults stored in fault memory
Air conditioner system OK
Engine running at idling speed

Test sequence

Switch on air conditioner system:
Manually controlled air conditioners: Press the "A/C" button.
Fully automatic air conditioners: Press the "AUTO" button, set the temperature to "LO" and the blower speed to "HI".

Briefly apply full throttle - the engine must reach its maximum speed.
Air conditioner compressor must stop for a few seconds (visual inspection)

If the air conditioner compressor is not switched off:

With the ignition switched off, use adapter V.A.G 1598/11 to connect test box V.A.G 1598 A to connector B only of engine control unit (control unit remains disconnected) => Page
24-10
.
Check for open circuit and short to positive or earth in the following wiring connections:

Test box / V.A.G 1598 A / socket · Control unit for magnetic coupling -J153 / contact · Operating and / display unit / -E87 / contact
21 · => "Current Flow Diagrams, Electrical Fault Finding and Fitting Locations" binder

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

=> Heater, Air conditioner; Repair group 87; Air conditioner; Servicing components of the manually controlled air conditioner
Heater, Air conditioner
Air conditioner
Servicing components of the manually controlled air conditioner

=> Heater, Air conditioner; Repair group 87; Air conditioner; Servicing components for controlling and regulating the fully automatic air conditioner
Heater, Air conditioner
Air conditioner
Servicing components for controlling and regulating the fully automatic air conditioner

If both air conditioner and wiring OK:

Replace engine control unit => Page
24-13
.