A12
De Dietrich
Fan Speed / Airflow Regulation Fault
Boiler shows A12, intermittent burner operation, sometimes with noise from fan
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Faulty fan speed sensor (Hall sensor) on De Dietrich fan, Blocked air intake, Loose fan speed feedback wiring, Defective main PCB speed control circuit
How to Fix / Troubleshooting
Safety: Turn off power before touching the fan or wiring.
Steps:
- Check air intake: Ensure the air intake path is clear and that the concentric flue is correctly assembled with no crushed sections.
- Inspect fan and wiring: Verify that the fan connector and any separate speed feedback wires are secure. Look for signs of overheating or corrosion.
- Clean fan wheel: Dust buildup can affect airflow. Carefully clean the fan blades with a soft brush and vacuum.
Professional help: Fan speed control issues usually require diagnostic tools. A technician may need to replace the fan or main PCB.
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Repair Difficulty
Hard
4/5
Required Part
Flue Fan Assembly
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