Volkswagen Workshop Service and Repair Manuals

Special tools, workshop equipment, 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 1551/3A
• ◆ Test box V.A.G 1598/22
• ◆ Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
• ◆ Adapter set V.A.G 1594
• ◆ Current flow diagram

Test conditions

• ● All electrical consumers, e.g. lights and rear window heating must be switched off.
• ● Air conditioner functioning OK.
• ● Air conditioner must be switched off
• ● Vehicle at room temperature (warmer than + 15 °C).
• ● No faults must be stored in fault memory , interrogating and erasing fault memory.

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 01-9 .)

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

• ‒ Press keys 0, 5 and 0 for "Display group number 50" and confirm entry with Q key.

• ‒ Observe display in display zone 3. It must show
       A/C-Low.
• ‒ Observe display in display zone 4. It must show
       Compr. OFF.

• ‒ Switch on air conditioning system.
• ‒ Select lowest temperature and highest blower speed.

• The display in display zone 3 must change to
       A/C-High.
• The display in display zone 4 must change to
       Compr. ON.

• ‒ Floor accelerator pedal quickly and then release (brief burst of throttle).

• The display in display zone 4 must change from
       Compr.ON
  to
       Compr. OFF
  for a few seconds (compressor switch-off when vehicle is accelerating).

• ‒ Press the ⇒key.
• ‒ Press keys 0 and 6 for the "End output" function and confirm input with the Q key.
• ‒ Switch off ignition.

If the display does not change:

• ‒ Remove wiper arms and cowl panel:

=> Electrical system; Repair group 92; windscreen wiper system; removing and installing windscreen wiper system

• ‒ → Connect test box V.A.G 1598/22 to control unit wiring harness.
• ‒ Check wiring for open circuit between test box sockets 17 + 42 and air conditioner using current flow diagram.
       Wire resistance: max. 1.5 ω

If no fault can be found in the wiring:

• ‒ Interrogate fault memory, if necessary, repair any faults and then erase fault memory => Page 01-18 , interrogating and erasing fault memory.
• ‒ Check function of air conditioner control unit.