How much does it cost to fix boiler error code S.33?

Typical repair cost for the boiler S.33 fault is £150-300 including labour.

S.33 High

Boiler Fault Code S.33

Also written as S33 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 31 August 2026

Fault code S.33 appears across 2 boiler brands and 26 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 an issue with the air pressure system needed for safe combustion and is keeping the internal fan running to clear any potentially harmful gases from the flue. (As reported on Glow-worm Easicom3 System)

Pick your boiler brand for the S.33 fix

Glow-worm S.33 13 models Vaillant S.33 13 models

Source

Information for the S.33 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 31 August 2026