BoilerFaultCodes F.673 Medium
Boiler Fault Code F.673
Also written as F673 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code F.673 appears across 1 boiler brand and 2 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler is having trouble communicating with the solar water heating system, which means it cannot properly monitor or control the sun-heated water supply. (As reported on Viessmann Vitodens 100-W WB1A)
Pick your boiler brand for the F.673 fix
Source
Information for the F.673 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