How much does it cost to fix boiler error code ON FLASH ON?

Typical repair cost for the boiler ON FLASH ON fault is £100-£180 including labour.

ON FLASH ON High

Boiler Fault Code ON FLASH ON

Also written as ONFLASHON — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code ON FLASH ON appears across 2 boiler brands and 28 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has detected a problem with its internal temperature sensor and has stopped working as a safety precaution. (As reported on Baxi Solo)

Pick your boiler brand for the ON FLASH ON fix

Baxi ON FLASH ON 24 models Potterton ON FLASH ON 4 models

Source

Information for the ON FLASH 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