BoilerFaultCodes S.3 Low
Boiler Fault Code S.3
Also written as S3 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code S.3 appears across 1 boiler brand and 26 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler is currently trying to start the ignition process to provide heating, which is a normal part of the startup sequence and not necessarily a fault unless it remains stuck on this screen. (As reported on Vaillant ecoMAX 613)
Pick your boiler brand for the S.3 fix
Source
Information for the S.3 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