BoilerFaultCodes L9 High
Boiler Fault Code L9
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code L9 appears across 2 boiler brands and 17 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler's internal computer has forgotten its settings or has developed a technical communication error, meaning it cannot safely control the heating process. (As reported on Ideal Logic+ System)
Pick your boiler brand for the L9 fix
Source
Information for the L9 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