35.S Low

Boiler Fault Code 35.S

Also written as 35S — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code 35.S appears across 1 boiler brand and 1 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 running a routine internal check to ensure everything is operating correctly and is not displaying an active fault. (As reported on Vaillant Thermocompact)

Pick your boiler brand for the 35.S fix

Vaillant 35.S 1 model

Source

Information for the 35.S 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