How much does it cost to fix boiler error code On Off On?

Typical repair cost for the boiler On Off On fault is £120-250 including labour.

On Off On High

Boiler Fault Code On Off On

Also written as ONOFFON — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 31 August 2026

Fault code On Off On appears across 2 boiler brands and 6 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has failed to light the flame properly and has shut itself down as a safety precaution while trying to start up. (As reported on Potterton Promax 15/2 HE Plus)

Pick your boiler brand for the On Off On fix

Baxi On Off On 2 models Potterton On Off On 4 models

Source

Information for the On Off 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 31 August 2026