BoilerFaultCodes Fast flash / Flashing High
Boiler Fault Code Fast flash / Flashing
Also written as FASTFLASHFLASHING — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code Fast flash / Flashing appears across 1 boiler brand and 4 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 serious fault and can no longer control the heating or hot water safely. (As reported on Worcester Bosch 28i Junior)
Pick your boiler brand for the Fast flash / Flashing fix
Source
Information for the Fast flash / Flashing 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