Audi Workshop Service and Repair Manuals

Notes:

• ◆ When the air conditioner is switched on, a positive signal is sent to contact 10 on the engine control unit.
• ◆ The signal causes the engine control unit to maintain a constant idling speed despite the varying power requirements of the air conditioner.

Test conditions

• ● Air conditioner functioning properly.
• ● No faults recorded in air conditioner fault memory.
• ● Passenger compartment temperature warmer than +15 °C.

• ‒ Connect the V.A.G. 1551 fault reader .
• ‒ Start the engine (operating temperature).
• ‒ Switch off the rear window heating.
• ‒ Select the function "Reading measured value block" (function 08) and Display Group 20 % Page.

Display zone 1: Idling speed

Display zone 3: Signal from air conditioner

Display zone 4: Signal from air conditioner compressor

• ‒ Switch on the air conditioner by pressing the "Auto" key. The compressor must run.

• Specification for display zone 4: "Compr. ON"

Apart from a brief drop in revs, the idling speed should remain constant.

If the idling speed does not remain constant, check whether the engine control unit is receiving the signal from the air conditioner.

• Specification for display zone 3: A/C - high
• Specification for display zone 4: "Compr. ON"

If the specified value is not achieved:

• ‒ Switch the ignition off.
• ‒ → Connect the V.A.G 1598/22 test box to the wiring harness for the engine control unit
  .
• ‒ Test for an open circuit and short to earth or positive in wiring from the contact 10 on engine control unit to the air conditioner.

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

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

=> Air conditioner; Repair Group 01; Self diagnosis for air conditioner