BoilerFaultCodes On Off On Off High
Boiler Fault Code On Off On Off
Also written as ONOFFONOFF — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code On Off On Off 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 has shut down because water intended for your drain is backing up and has triggered a safety sensor. (As reported on Potterton Promax FSB 30HE)
Pick your boiler brand for the On Off On Off fix
Source
Information for the On Off On Off 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