F.27 error: the boiler attempts to ignite but locks out, sometimes with a smell of gas at the flue.
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.
Possible Causes
How to Fix / Troubleshooting
Safety: Turn off the gas and power immediately if you suspect gas leakage. Ventilate the area and do not use open flames.
Checks (qualified personnel recommended):
- Inspect the ionization electrode for cracks, soot, or incorrect position relative to the burner; clean or replace as needed.
- Check the electrode cable and connection to the PCB for damage or tracking.
- Test the gas valve for tightness when closed; replace if it allows gas flow when de-energized.
- Verify correct earthing of the boiler, as poor earthing can affect flame detection.
Note: Persistent F.27 requires professional diagnosis due to the risk of unsafe combustion.
Repair Difficulty
Required Part
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