Additional Heating

Fault code 0668

Vehicle voltage, terminal 30

Diagnostic conditions
- Engine on
- Internal auxiliary heater control unit function test

Possible cause of fault
- Above upper limit (vehicle electrical system voltage, terminal 30 with engine running over 15.8 V)
- Auxiliary heater control unit faulty

Affected pins
Plug B for auxiliary heater control unit
- Pin 1 'terminal 30'
- Pin 2 'terminal 31'

Diagnosis/troubleshooting

WARNING: Danger of accident due to moving parts when working in engine compartment

NOTE:
Visual inspection: During the next check, first ensure that the affected pins of the 14-pin plug connection on the wiring harness are neither damaged nor corroded. Remove any soiling or corrosion/oxidation. Replace damaged parts/wires.

NOTE:
Battery voltage: A battery voltage of between 11.4 and 14.5 V is required for the following troubleshooting procedure. This must be checked and provided, if necessary. On the vehicle electrical system, the voltage to the fuse (input side) must be guaranteed.