BoilerFaultCodes F42 – A42 High
Boiler Fault Code F42 – A42
Also written as F42A42 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code F42 – A42 appears across 1 boiler brand and 3 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 inconsistent temperature reading between its internal sensors and has shut down to prevent overheating. (As reported on Ferroli iBoiler 28)
Pick your boiler brand for the F42 – A42 fix
Source
Information for the F42 – A42 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