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

Typical repair cost for the boiler Flash On On fault is £250-400 including labour.

Flash On On High

Boiler Fault Code Flash On On

Also written as FLASHONON — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 31 August 2026

Fault code Flash On On appears across 3 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 computer has developed a fault and is unable to operate, meaning the system will not provide any heating or hot water until a professional repairs it. (As reported on Potterton Promax 15/2 HE Plus)

Pick your boiler brand for the Flash On On fix

Baxi Flash On On 2 models Main Flash On On 1 model Potterton Flash On On 2 models

Source

Information for the 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 31 August 2026