Boiler Fault Code L1

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

Fault code L1 appears across 4 boiler brands and 34 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 because the internal water temperature has become too hot, usually caused by a lack of water flow through the system. (As reported on Ideal Logic Code Combi ESP1)