Boiler Fault Code Lockout (Red) light flash

Also written as LOCKOUTREDLIGHTFLASH — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026

Fault code Lockout (Red) light flash appears across 1 boiler brand and 1 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has automatically turned itself off because internal sensors detected it was getting too hot, likely due to a flow restriction or a faulty sensor. (As reported on Potterton Performa SL HE 9 2)