BoilerFaultCodes Red light flashing (Lockout) High
Boiler Fault Code Red light flashing (Lockout)
Also written as REDLIGHTFLASHINGLOCKOUT — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code Red light flashing (Lockout) appears across 1 boiler brand and 2 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler has failed to start up or stay lit and has now shut itself down for safety, meaning you currently have no heating or hot water. (As reported on Potterton Suprima HE)
Pick your boiler brand for the Red light flashing (Lockout) fix
Source
Information for the Red light flashing (Lockout) 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