How much does it cost to fix boiler error code S.109?

Typical repair cost for the boiler S.109 fault is £0-80 including labour.

S.109 Low

Boiler Fault Code S.109

Also written as S109 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code S.109 appears across 1 boiler brand and 14 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has temporarily stopped working because it has entered a standby mode, usually while it waits for a signal from your thermostat or because it needs to take a short break before restarting. (As reported on Vaillant ecoTEC plus)

Pick your boiler brand for the S.109 fix

Vaillant S.109 14 models

Source

Information for the S.109 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