BoilerFaultCodes S.42 High
Boiler Fault Code S.42
Also written as S42 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code S.42 appears across 2 boiler brands and 38 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler has temporarily stopped heating because an external add-on or control accessory is preventing it from firing up. (As reported on Glow-worm Ultracom 2 SXI)
Pick your boiler brand for the S.42 fix
Source
Information for the S.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 27 April 2026