BoilerFaultCodes F63 High
Boiler Fault Code F63
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code F63 appears across 2 boiler brands and 17 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler's main internal computer has developed a communication failure, meaning it can no longer control the heating and hot water functions. (As reported on Glow-worm Flexicom 18sx)
Pick your boiler brand for the F63 fix
Source
Information for the F63 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