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Audi Workshop Service and Repair Manuals

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Testing clutch pedal switch > < Test signals from and to automatic gearbox

A3 Mk1

Diesel Direct Injection and Glow Plug System (TDI 4 cyl.) >07.99
Checking auxiliary signals
Checking signals from / to air conditioner

Checking the air conditioner compressor shutoff

The engine control unit will shut off the air conditioning compressor in the following cases:

  • ◆ Heavy acceleration from low speeds (control unit detects angle change at sensor for accelerator pedal position and receives road speed signal)
  • ◆ In the emergency programme (emergency running mode)
  • ◆ If coolant temperature is above 120 °C
  • ◆ After every start, for approx. 6 seconds.

Test conditions

  • ● Air conditioning system OK
  • ● Air conditioner switched on
  • ● No fault stored in fault memory
 
→ Start final control diagnosis and activate exhaust gas recirculation start valve .
Final control diagnosis    

The AC compressor must come to a stop within 5 s (visual inspection) and then start up and stop again every 5 s.

If the conditioner compressor is not switched off:

  • ‒ Connect test box V.A.G 1598/22 to wiring harness for engine control unit .

The following wiring connections are to be checked for open circuits and/or short to positive or negative.

Test box V.A.G 1598/22, socket

Air conditioner operating and display unit, contact

16

=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations
  • ‒ Rectify any open/short circuit as necessary.

Checking air conditioner signal

The air conditioner signal informs the engine control unit that the air conditioner needs a higher idling speed in order to provide the desired interior temperature (both when cooling and heating).

The increase in idling speed resulting from the air conditioner signal depends on the control unit version and is not activated in all vehicles.

  • ‒ Read measured value block, display group 02, engine at idling speed => Page 01-66
 
→ Indicated on display:
Read measured value block 2    ⇒
    900 rpm    0.0 %    0    1    0    18.4 5C
  • ‒ Switch on air conditioner, press the "Auto" key and select the lowest temperature.
  • ‒ Check display in display zone 3.
 
→ Specification: X X 1 (AC compressor signal)
Read measured value block 2    ⇒
    900 rpm    0.0 %    1    1    1    18.4 5C

If specified value is not attained:

  • ‒ Connect test box V.A.G 1598/22 to wiring harness for engine control unit .

The following wiring connections are to be checked for open circuits and/or short to positive or negative.

Test box V.A.G 1598/22, socket

Air conditioner operating and display unit, contact

48

=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations
  • ‒ Rectify any open/short circuit as necessary.

Testing clutch pedal switch > < Test signals from and to automatic gearbox