Heating/Ventilation

Special tool
Adaptor for testing resistance and 126 589 042 100
voltage supply


NOTE: The test program should be performed for unknown faults, unclear customer complaints and following repairs to check all functions.

The fuses for the automatic heating system as well as the heater blower must be checked and the battery voltage in proper working order before commencing the following test.

B. Test program

















NOTE: Switch Off ignition for all further tests.







The position of the respective temperature selector of last test is simultaneously the starting point for the next-following test step.




























































































B. Test program short against ground

1 Remove fuse for automatic heater from fuse box.







2 Set both temperature selectors (2 and 3) for automatic heater to 22 °C.
3 Connect one test prod of ohmmeter to terminal 6 (ground) of 12-pole coupler for electronic switching unit (9) of automatic heater.
4 With other test prod, measure resistance on terminals 1 to 5 and 7 to 12 one after the other.
Nominal value measured at terminals 1 to 4 and 7 to 11 = 20 kOhms to Infinity.
5 If at one of the tests another value has been measured than named in nominal values, recondition respective line according to wiring diagram and renew harness, as required.







Electric wiring diagram for automatic heater
1 In-car temperature sensor
2 Temperature selector left
3 Temperature selector right
4 Air flow switch
5 Main fuse box
Fuse 10:16 Amps.
Fuse 11:25 Amps.
6 Temperature sensor left for heat exchanger
7 Temperature sensor for heat exchanger
8 Dual heating water valve
9 Electronic switching unit with relay for auxiliary heating water pump
10 Auxiliary heating water pump (not on vehicles with engine 110)
11 Blower motor
12 Pre-resistance group
a Terminal 58 d