BoilerFaultCodes A42 High
Boiler Fault Code A42
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code A42 appears across 1 boiler brand and 7 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 unusual temperature difference between its sensors and has shut down to prevent any internal damage. (As reported on Ferroli Bluehelix Tech)
Pick your boiler brand for the A42 fix
Source
Information for the 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