C1
Junkers
Fan / Air Pressure Switch Fault
Fan starts but unit locks out with C1; no ignition or very short ignition attempt.
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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 motor, Blocked air pressure tubing, Defective air pressure switch, Blocked flue or intake causing incorrect pressure
How to Fix / Troubleshooting
Safety: Isolate electrical power and gas before removing the combustion cover. The flue system is critical for safe operation.
- Check flue terminal: Ensure the outside terminal is not blocked by debris, snow, or nests.
- Inspect fan: Remove the front cover and visually inspect the fan. Spin the impeller gently by hand; it should rotate freely without scraping.
- Clean pressure tubes: Locate the silicone tubes between the fan/combustion chamber and the air pressure switch. Remove them and blow through to clear condensate or dust. Refit securely.
- Check pressure switch wiring: Ensure the connectors on the air pressure switch are tight and not corroded.
- Test run: Restore power and attempt a start. If C1 persists, the fan or pressure switch may need replacement by a qualified technician.
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Repair Difficulty
Hard
4/5
Required Part
Fan Assembly or Air Pressure Switch
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