F.27
Flame signal detected while burner is off
The boiler control has detected a flame signal when the burner should not be operating.
What this code means
The boiler control has detected a flame signal when the burner should not be operating.
Possible causes
- Gas solenoid valve not sealing correctly
- PCB fault
Common symptoms
- F.27 displayed
- Boiler locks out or refuses normal operation
Checks to make
- Do not repeatedly reset the boiler
- Arrange professional diagnosis
Safety
- This is a combustion/gas safety fault. Do not remove the boiler casing or attempt gas-valve repairs yourself.
Model notes
Vaillant identifies gas-valve leakage or PCB failure as possible causes.