BoilerFaultCodes F.42 High
Boiler Fault Code F.42
Also written as F42 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code F.42 appears across 2 boiler brands and 9 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 a problem with the internal wiring that sends signals between its control components, meaning it cannot operate safely and has shut itself down. (As reported on Vaillant Turbomax 824/828)
Pick your boiler brand for the F.42 fix
Source
Information for the F.42 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 31 August 2026