How much does it cost to fix boiler error code S.31?

Typical repair cost for the boiler S.31 fault is £0-120 including labour.

S.31 Low

Boiler Fault Code S.31

Also written as S31 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 7 July 2026

Fault code S.31 appears across 3 boiler brands and 74 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 set to its summer setting or is being told by your thermostat not to turn on the heating because it thinks the house is warm enough. (As reported on Vaillant ecoTEC exclusive)

Pick your boiler brand for the S.31 fix

Glow-worm S.31 30 models Heatline S.31 7 models Vaillant S.31 37 models

Source

Information for the S.31 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