F7
Junkers
Flame Detected When There Should Be None
Error F7, furnace does not start, sometimes after power outage
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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
Shorted ionisation electrode to burner, Faulty control board flame circuit, Residual flame due to gas valve not closing fully, Incorrect grounding
How to Fix / Troubleshooting
Safety first: Turn off gas and power immediately. A flame present when there should be none is dangerous.
- 1. Visual inspection: Check through the inspection window that there is no actual flame when the furnace is idle. If a flame is present, shut off gas at the main cock and call a professional immediately.
- 2. Electrode check: Inspect the ionisation electrode for damage or carbon tracking that could cause a false flame signal. Ensure it is not touching the burner metal.
- 3. Wiring and grounding: Verify that the ionisation cable is not shorted to ground and that all earth connections are secure.
- 4. Gas valve closure: A technician should verify that the gas valve fully closes when de-energised. If it leaks, the valve must be replaced.
- 5. Control board: If no actual flame or wiring fault is found, the PCB flame detection circuit may be defective and require replacement.
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Repair Difficulty
Professional Required
5/5
Required Part
Gas Valve Assembly
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