Signal Too High

Signal too high

Checking the function of the combustion fan

Note! On cars where the heater functions as a parking heater there is no +15 voltage supply to the control module. Individual components and functions cannot be activated when the +15 voltage supply is absent.




- Ignition on
- Activate the combustion fan.
Listen for a buzzing sound which indicates that the combustion fan is running.





Does the combustion fan function?

Yes - Intermittent fault

No - Checking components and wiring

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Checking components and wiring
Check the cable between control module terminal #10 and the signal terminal for the combustion fan (the black lead from the fan). Check for a short-circuit to supply voltage according to Checking wiring and terminals. Permanent fault Checking Wiring And Terminals. Permanent Fault.
If no faults are found in the cable, the combustion fan must be replaced according to Replacing fuel injection nozzle, fan motor and nozzle pipe Service and Repair.
Remedy as necessary.

Other information:
- To access the control module or connect the breakout box, see
- Remove the heater according to Replacing heat exchanger Service and Repair to access the combustion fan. Remove the fan shroud
- With the ignition on and the combustion fan signal connection disconnected, the voltage between the combustion fan signal terminal (control module side) and ground should be approximately 0 V
- For other values, see Signal specification Additional heater 912-D/B Signal Specification Additional Heater 912-D/B.













Select Continue.

Continue - Verification

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Verification




Verification

Verification

Hint: After carrying out the repair, check that the fault has been remedied.

Note! On cars where the heater functions as a parking heater there is no +15 voltage supply to the control module. Individual components and functions cannot be activated when the +15 voltage supply is absent.








- Ignition off
- Reinstall the connectors, components etc.
- Ignition on
- Activate the combustion fan.
Listen for a buzzing sound which indicates that the combustion fan is running.





Does the combustion fan function?

Yes - VERIFIED

No - VERIFICATION FAILEDPAPER

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VERIFIED - FAULT FOUND

VERIFICATION FAILED - Fault-tracing information

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Fault-tracing information




Information

Fault-tracing information
The fault should have been detected and remedied. As this is not the case fault-tracing has failed.
Exit fault-tracing for this diagnostic trouble code (DTC) or make another attempt.

Do you want to exit fault-tracing?

Yes - FAULT-TRACING FAILED

No - Attempt New Test

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FAULT-TRACING FAILED - FAULT-TRACING FAILED

Attempt New Test - Checking the function of the combustion fan

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Intermittent fault
Check the cable between control module terminal #10 and the signal terminal for the combustion fan (the black lead from the fan). Check for a short-circuit to supply voltage according to Checking wiring and terminals. Intermittent faults Checking Wiring And Terminals. Intermittent Faults.
Remedy as necessary.

Other information:
- To access the control module or connect the breakout box, see
- Remove the heater according to Replacing heat exchanger Service and Repair to access the combustion fan. Remove the fan shroud
- With the ignition on and the combustion fan signal connection disconnected, the voltage between the combustion fan signal terminal (control module side) and ground should be approximately 0 V
- For other values, see Signal specification Additional heater 912-D/B Signal Specification Additional Heater 912-D/B.













Select Continue.

Continue - Fault-tracing information
DONE

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Fault-tracing information




Information

Fault-tracing information
If the fault is intermittent, do not verify fault-tracing if the fault does not recur.
It is possible to view the information again, or leave fault-tracing for this diagnostic trouble code (DTC).

Do you want to view the information again?

Yes - Attempt New Test

No - FAULT FOUND

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Attempt New Test - Checking the function of the combustion fan

FAULT-TRACING FAILED - DONE

FAULT FOUND - FAULT FOUND

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