BoilerFaultCodes 9 flashes High
Boiler Fault Code 9 flashes
Also written as 9FLASHES — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 9 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's internal computer has encountered a critical communication error and can no longer control the heating process safely. (As reported on Worcester Bosch Greenstar 25CDi)
Pick your boiler brand for the 9 flashes fix
Source
Information for the 9 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