Lights: Flash On On High

Boiler Fault Code Lights: Flash On On

Also written as LIGHTSFLASHONON — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code Lights: Flash On On appears across 2 boiler brands and 5 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler’s internal control system has detected a critical electronic failure, meaning it can no longer safely operate or heat your home. (As reported on Potterton Promax HE Store)

Pick your boiler brand for the Lights: Flash On On fix

Baxi Lights: Flash On On 2 models Potterton Lights: Flash On On 3 models

Source

Information for the Lights: Flash On 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