S.01 Low

Boiler Fault Code S.01

Also written as S01 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code S.01 appears across 4 boiler brands and 56 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler is preparing to start the heating process by running the internal fan to clear out the combustion chamber. (As reported on Glow-worm Ultracom 24cx 30cx)

Pick your boiler brand for the S.01 fix

Ariston S.01 5 models Glow-worm S.01 12 models Heatline S.01 8 models Vaillant S.01 31 models

Source

Information for the S.01 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