BoilerFaultCodes F09 L09 High
Boiler Fault Code F09 L09
Also written as F09L09 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code F09 L09 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's main control board has lost its programmed settings and no longer knows how to operate the specific model it is installed in. (As reported on Ideal Logic Code Combi ESP1)
Pick your boiler brand for the F09 L09 fix
Source
Information for the F09 L09 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