How much does it cost to fix boiler error code Lock-out (light on)?

Typical repair cost for the boiler Lock-out (light on) fault is £120-250 including labour.

Lock-out (light on) High

Boiler Fault Code Lock-out (light on)

Also written as LOCKOUTLIGHTON — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code Lock-out (light on) appears across 1 boiler brand and 5 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has stopped itself from running as a safety precaution because the fuel failed to ignite properly. (As reported on Grant Vortex Eco)

Pick your boiler brand for the Lock-out (light on) fix

Grant Lock-out (light on) 5 models

Source

Information for the Lock-out (light on) 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