Volkswagen Workshop Service and Repair Manuals

These signals from the air conditioner cause the initial control value for the idling stabilization to be increased when the air conditioner compressor switches in. Thereby the idling stabilization remains in the middle of the regulating range.

Special tools, testers, measuring instruments and auxiliary items required

• ◆ Fault reader V.A.G 1551 or vehicle system tester V.A.G 1552 with cable V.A.G 1551/3
• ◆ Test box V.A.G 1598/18
• ◆ Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
• ◆ Adapter set V.A.G 1594
• ◆ Current flow diagram

Test conditions

• ● Air conditioner functioning OK.
• ● Air conditioner must be switched off
• ● No faults must be stored in fault memory
  , interrogating fault memory
• ● Vehicle at room temperature (warmer than + 15 °C).

Test sequence

• ‒ Connect fault reader V.A.G 1551 (V.A.G 1552). Start engine and select "Address word" 01 of engine control unit. When doing this the engine must be running at idling speed.
  (Connecting fault reader and selecting engine control unit => Page 01-4 .)

• ‒ Press keys 0 and 8 for the function "Read measured value block" and confirm entry with Q key.

• ‒ Press keys 0 and 1 for "Display group number 01" and confirm entry with Q key.

• ‒ Observe 8 digit number block in display zone 4. 3rd position from left must display 0.
       Display: 00000000
• ‒ Switch on air conditioner. Adjust lowest temperature and highest blower stage.

• 3rd position from left must now display 1
       Display: 00100000

If the display does not change:

• ‒ → Connect test box V.A.G 1598/18 to control unit wiring loom.

• ‒ Check wiring between test box sockets 33 and 35 and the air conditioner for open circuit according to current flow diagram.
       Wire resistance: Max. 1.5 ω