ON Low

Boiler Fault Code ON

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code ON appears across 3 boiler brands and 4 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler is operating normally and successfully maintaining a flame, meaning everything is working exactly as it should. (As reported on Potterton Prima 30B)

Pick your boiler brand for the ON fix

Ariston ON 1 model Biasi ON 1 model Potterton ON 2 models

Source

Information for the ON 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