How much does it cost to fix boiler error code 40 ❍, yellow ❍?

Typical repair cost for the boiler 40 ❍, yellow ❍ fault is £120-200 including labour.

40 ❍, yellow ❍ High

Boiler Fault Code 40 ❍, yellow ❍

Also written as 40YELLOW — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code 40 ❍, yellow ❍ appears across 1 boiler brand and 1 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has lost the ability to measure the temperature of the water being sent to your radiators, so it has shut down to protect the system. (As reported on Ariston Clas One)

Pick your boiler brand for the 40 ❍, yellow ❍ fix

Ariston 40 ❍, yellow ❍ 1 model

Source

Information for the 40 ❍, yellow ❍ 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