Boiler Fault Code Fast flash / Not a fault code

Also written as FASTFLASHNOTAFAULTCODE — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026

Fault code Fast flash / Not a fault code appears across 1 boiler brand and 1 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler is currently stuck in a manual testing mode used by engineers and needs to be switched back to its normal operating setting. (As reported on Worcester Bosch Greenstar i Junior)