Signal Too Low

Signal too low

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 the connectors

-------------------------------------------------

Checking the connectors








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

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.





Does the combustion fan function?

Yes - FAULT FOUND

No - Checking components and wiring

-------------------------------------------------

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 an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring And Terminals. Permanent Fault. Check for a short-circuit to ground according to Checking wiring and terminals. Permanent fault Checking Wiring And Terminals. Permanent Fault.
Check the cable between control module terminal #11 and the voltage terminal for the combustion fan (the red cable from the fan). Check for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring And Terminals. Permanent Fault.
If no faults are found in the wiring, the combustion fan must 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 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
- For other values, see Signal specification Additional heater 912-D/B Signal Specification Additional Heater 912-D/B.













Select Continue.

Continue - Verification

-------------------------------------------------

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

------------------------

VERIFICATION FAILED - Fault-tracing information

VERIFIED - FAULT FOUND

-------------------------------------------------

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

------------------------

FAULT-TRACING FAILED - FAULT-TRACING FAILED

Attempt New Test - Checking the function of the combustion fan

-------------------------------------------------

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

-------------------------------------------------

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

------------------------

Attempt New Test - Checking the function of the combustion fan

DONE - DONE

FAULT FOUND - FAULT FOUND

-------------------------------------------------