Boiler Fault Code F9 C

Also written as F9C — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026

Fault code F9 C appears across 1 boiler brand and 1 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has lost its internal settings and no longer knows it is supposed to function as a combination boiler providing both heating and hot water. (As reported on Ideal i-mini2 C24)