F09 High

Boiler Fault Code F09

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code F09 appears across 3 boiler brands and 4 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 developed a fault and can no longer control the heating or hot water safely. (As reported on Ideal Logic Max System)

Pick your boiler brand for the F09 fix

Ferroli F09 2 models Ideal F09 1 model Viessmann F09 1 model

Source

Information for the F09 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 7 July 2026