BoilerFaultCodes S.39 Medium
Boiler Fault Code S.39
Also written as S39 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code S.39 appears across 1 boiler brand and 39 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler has paused because it detected that the water temperature is too high for your underfloor heating system, triggered by a safety safety switch to protect your floors. (As reported on Vaillant ecoMAX 613)
Pick your boiler brand for the S.39 fix
Source
Information for the S.39 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 27 April 2026