BoilerFaultCodes 3 flashes Medium
Boiler Fault Code 3 flashes
Also written as 3FLASHES — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 3 flashes appears across 2 boiler brands 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 hot water temperature sensor has stopped working, which means the system cannot accurately heat your water. (As reported on Worcester Bosch Greenstar 25CDi)
Pick your boiler brand for the 3 flashes fix
Source
Information for the 3 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 31 August 2026