Boiler Fault Code Red LED (Lockout)

Also written as REDLEDLOCKOUT — same fault.

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

Fault code Red LED (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 automatically shut down for safety because it has detected a blockage in the chimney or flue that prevents dangerous exhaust gases from escaping. (As reported on Potterton Kingfisher MF 40-100)