BoilerFaultCodes 4 (Flashing Light) Low
Boiler Fault Code 4 (Flashing Light)
Also written as 4FLASHINGLIGHT — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 4 (Flashing Light) appears across 1 boiler brand and 9 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 idle and waiting for a signal to provide heating or hot water, so it is simply in 'standby' mode and functioning as expected. (As reported on Ferroli Domina 102)
Pick your boiler brand for the 4 (Flashing Light) fix
Source
Information for the 4 (Flashing Light) 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