BoilerFaultCodes LED4 flashing High
Boiler Fault Code LED4 flashing
Also written as LED4FLASHING — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code LED4 flashing appears across 1 boiler brand and 7 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler is struggling to detect water moving through the system, which prevents it from safely firing up to heat your home or provide hot water. (As reported on Ferroli Falcon)
Pick your boiler brand for the LED4 flashing fix
Source
Information for the LED4 flashing 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