BoilerFaultCodes F.321 High
Boiler Fault Code F.321
Also written as F321 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code F.321 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 detected that the water pump responsible for circulating heat is not working correctly, which means the system cannot provide heating or hot water. (As reported on Vaillant ecoTEC Plus 832)
Pick your boiler brand for the F.321 fix
Source
Information for the F.321 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