BoilerFaultCodes F.378 High
Boiler Fault Code F.378
Also written as F378 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code F.378 appears across 1 boiler brand 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 has detected an issue with the fuel-air mixture during the ignition process, meaning it cannot safely start the burner to provide heating or hot water. (As reported on Viessmann Vitodens 200-W B2KF Combi)
Pick your boiler brand for the F.378 fix
Source
Information for the F.378 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