BoilerFaultCodes F.9 High
Boiler Fault Code F.9
Also written as F9 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code F.9 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 has lost connection with the sensor that measures the temperature of your hot water, meaning the system cannot safely heat water for your taps. (As reported on Viessmann Vitodens 200-W B2KF Combi)
Pick your boiler brand for the F.9 fix
Source
Information for the F.9 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