BoilerFaultCodes L- High
Boiler Fault Code L-
Also written as L — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code L- appears across 1 boiler brand and 3 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler has switched itself off for safety and is displaying a 'lockout' status, which will be accompanied by a second flashing code to tell you exactly what is wrong. (As reported on Ideal Isar System)
Pick your boiler brand for the L- fix
Source
Information for the L- 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