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Checking the air conditioner compressor shutoff > < Checking auxiliary signals

A4 Mk1

MPFI Fuel Injection and Ignition System
Checking auxiliary signals
Checking heated rear window signal

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
  • or
  • ◆ V.A.G 1551 with V.A.G 1551/3 A

Note:

On vehicles with no air conditioner, voltage is applied to contact B11 of engine control unit when heated rear window is switched on. This increases the idling speed for a higher charging rate.

  • ‒ Read measured value block, Display Group 006, engine at idling speed.
 
→ Indicated on display:
Read measured value block 6    ⇒
    1    2    3    4
  • ‒ Check display in display zone 3.
  • ‒ Switch off the heated rear window.
 
A87-0016
    • ‒ Value must be incremented 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 .
  • ‒ Connect voltage tester V.A.G 1527 B as follows:

Test box V.A.G 1598 A
Socket

Measure to

31

Engine earth
  • ‒ Switch on ignition and heated rear window.
    • ‒ The LED should light up.

If the LED does not light up:

  • ‒ Pull off adapter V.A.G 1598/11 at engine control unit position B.

If the LED then lights up:

  • ‒ Replace engine control unit => Page 24-12.

If LED still does not light:

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

Test box
V.A.G 1598 A
Socket

Heated rear window
switch
Contact

31

=> "Current Flow Diagrams, Electrical Fault Finding and Fitting Locations" binder

If the wiring is OK:

  • ‒ Check the heated rear window.

Checking the air conditioner compressor shutoff > < Checking auxiliary signals