S.34 Low

Boiler Fault Code S.34

Also written as S34 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code S.34 appears across 4 boiler brands and 83 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has detected very cold temperatures and is running its internal pump to prevent the water inside from freezing. (As reported on Vaillant ecoTEC 65kW)

Pick your boiler brand for the S.34 fix

British Gas S.34 1 model Glow-worm S.34 29 models Heatline S.34 7 models Vaillant S.34 46 models

Source

Information for the S.34 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