BoilerFaultCodes F42 High
Boiler Fault Code F42
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code F42 appears across 2 boiler brands and 11 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler has detected an issue with one of its internal sensors, preventing it from safely controlling your heating and hot water. (As reported on Glow-worm Flexicom 18sx)
Pick your boiler brand for the F42 fix
Source
Information for the F42 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