How much does it cost to fix boiler error code S.42?

Typical repair cost for the boiler S.42 fault is £60-180 including labour.

S.42 High

Boiler Fault Code S.42

Also written as S42 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 31 August 2026

Fault code S.42 appears across 3 boiler brands and 65 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 providing heating or hot water because an external control or smart accessory is preventing it from firing up. (As reported on Glow-worm Flexicom cx)

Pick your boiler brand for the S.42 fix

British Gas S.42 1 model Glow-worm S.42 25 models Vaillant S.42 39 models

Source

Information for the S.42 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