BoilerFaultCodes Fn High
Boiler Fault Code Fn
Also written as FN — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code Fn appears across 1 boiler brand and 5 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler has lit correctly but the flame has gone out unexpectedly, often due to a temporary interruption in the gas supply or a blocked condensate pipe. (As reported on Ideal Logic Combi C24 C30 C35)
Pick your boiler brand for the Fn fix
Source
Information for the Fn fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026