audi Workshop Repair Guides

Audi Workshop Service and Repair Manuals

ABOUT US
Testing engine speed adaptation when air conditioner cuts in > < Testing auxiliary signals

A3 Mk1

Simos Injection and Ignition System (4-cylinder)
Testing auxiliary signals
Testing air conditioner compressor shut-off

Notes:

  • ◆ The air conditioner compressor signal from the operating and display unit informs the engine control unit that the compressor is due to cut in shortly.
  • ◆ The engine control unit can send a signal via the same wire to shut off the air conditioner compressor.
  • ◆ On vehicles with manual gearbox the air conditioner compressor is shut off at full throttle in first gear.
  • ◆ On vehicles with automatic gearbox there is no air conditioner compressor shut-off.

Test conditions

  • ● Air conditioner functioning properly
  • ● No faults recorded in fault memory of engine control unit
  • ● Interior temperature of more than +15 °C
  • ‒ Connect fault reader V.A.G 1551 .
  • ‒ Start the engine.
  • ‒ Select "Read measured value block" (function 08) and Display Group 19.
  • ‒ Switch off air conditioner.
 
→ Display readout:
Read measured value block 19    ⇒
    X    X    0    0

Display zone 3 should read "0" (air conditioner operating status).

Display zone 4 should read "0" (air conditioner compressor).

  • ‒ Switch on air conditioner by pressing "Auto" key and selecting the lowest temperature. The air conditioner compressor should run.
 
→ Display readout:
Read measured value block 19    ⇒
    X    X    1    1

Display zone 3 should read "1" (air conditioner operating status).

Display zone 4 should read "1" (air conditioner compressor).

  • ‒ Take vehicle for a test drive in first gear (press down sharply on accelerator at low engine speed).
Important!
The V.A.G 1551 must be operated by a second person.
 
→ Display readout:
Read measured value block 19    ⇒
    X    X    1    0

When accelerating, display zone 4 should read "0" (the air conditioner compressor is switched off during acceleration).
 
A28-0022
  • ‒ → If the readouts are not as specified, switch off the engine and connect test box V.A.G 1598/22 to wiring harness for engine control unit => Page 24-8.
  • ‒ Using current flow diagram, test for open circuit and short to earth or positive in wiring between air conditioner operating and display unit (E87) and contact 8 on engine control unit.

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

  • ‒ If there are no faults in the wiring, test operation of air conditioner operating and display unit (-E87).

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

Testing engine speed adaptation when air conditioner cuts in > < Testing auxiliary signals