BoilerFaultCodes On / Off (CH fault) Medium
Boiler Fault Code On / Off (CH fault)
Also written as ONOFFCHFAULT — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code On / Off (CH fault) appears across 1 boiler brand and 1 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler is failing to switch on for heating even though your hot water is working perfectly fine. (As reported on Worcester Bosch Greenstar i Junior)
Pick your boiler brand for the On / Off (CH fault) fix
Source
Information for the On / Off (CH fault) 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