BoilerFaultCodes 5 flashes High
Boiler Fault Code 5 flashes
Also written as 5FLASHES — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 5 flashes appears across 1 boiler brand and 3 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler has identified that the fan responsible for clearing exhaust fumes is not spinning at the correct speed, preventing it from starting safely. (As reported on Worcester Bosch Greenstar 25CDi)
Pick your boiler brand for the 5 flashes fix
Source
Information for the 5 flashes 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