Signal Too Low

Signal too low

Checking combustion fan function




- Ignition on.
- Activate 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 the connectors

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Checking the connectors








- Ignition off.
- Remedy combustion fan electrical terminals and control module connector for contact resistance and oxidation according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Check any damage etc.
- Reinstall components, reconnect connectors etc.
- Ignition on.
- Activate combustion fan.
Listen for a buzzing sound which indicates that the combustion fan is running.
If the combustion fan now operates it means that the cause of the fault has been loose connections in the connectors.

Other information:
- To access the control module/connect breakout box see.
- To access the combustion fan, position heater in service mode according to Moving the heater to its service position Procedures and remove fan shroud.





Does the combustion fan function?

Yes - FAULT FOUND

No - Checking component and cables

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Checking component and cables
Check cable between control module #10 and combustion fan signal terminal (black cable from fan) for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault and a short-circuit to ground according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Check cable between control module #11 and combustion fan voltage terminal (red cable from fan) for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
If no fault is found in the cables the combustion fan should be replaced according to Replacing fuel injection nozzle, fan motor and nozzle pipe Service and Repair.

Note! Diagnostic trouble code (DTC) HEA-821 water pump signal and/or diagnostic trouble code (DTC) HEA-825 fuel pump (FP), signal can be stored in case of faults in the power cable.

Remedy as necessary.

Other information:
- To access the control module/connect breakout box see.
- To access the combustion fan, position heater in service mode according to Moving the heater to its service position Procedures and remove fan shroud.
- For other values, see Signal specification Additional heater 912-D/B Signal Specification Additional Heater 912-D/B.













Continue - Verification

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Verification




Verification

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








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





Does the combustion fan function?

Yes - VERIFIED

No - VERIFICATION FAILED

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VERIFICATION FAILED - Fault-tracing information

VERIFIED - FAULT FOUND

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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 - Exit fault-tracing

No - Attempt New Test

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Attempt New Test - Checking combustion fan function

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Intermittent fault
Check combustion fan electrical terminals and control module connector for contact resistance and oxidation according to Checking wiring and terminals. Intermittent faults Checking Wiring and Terminals. Intermittent Faults.
Check cable between control module #10 and combustion fan signal terminal (black cable from fan) for an intermittent open-circuit according to Checking wiring and terminals. Intermittent faults Checking Wiring and Terminals. Intermittent Faults and an intermittent short-circuit to ground according to Checking wiring and terminals. Intermittent faults Checking Wiring and Terminals. Intermittent Faults.
Check cable between control module #11 and combustion fan supply terminal (red cable from fan) for an intermittent open-circuit according to Checking wiring and terminals. Intermittent faults Checking Wiring and Terminals. Intermittent Faults.
Remedy as necessary.

Other information:
- To access the control module/connect breakout box see.
- To access the combustion fan, position heater in service mode according to Moving the heater to its service position Procedures and remove fan shroud.
- For other values, see Signal specification Additional heater 912-D/B Signal Specification Additional Heater 912-D/B.













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 combustion fan function

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