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

Typical repair cost for the boiler ON OFF FLASH fault is £80-160 including labour.

ON OFF FLASH High

Boiler Fault Code ON OFF FLASH

Also written as ONOFFFLASH — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code ON OFF FLASH 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 that the electrical wiring coming into the unit is connected the wrong way around, causing it to shut down for safety. (As reported on Baxi Solo)

Pick your boiler brand for the ON OFF FLASH fix

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

Source

Information for the ON OFF FLASH 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