Boiler Fault Code S.26

Also written as S26 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026

Fault code S.26 appears across 4 boiler brands and 57 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler's internal cooling fan is staying on longer than expected after a heating cycle to ensure any remaining gases are cleared. (As reported on Vaillant ecoTEC plus Regular)