40 ❍, 50 ❍, 60 ❍, yellow ❍ Medium
Boiler Fault Code 40 ❍, 50 ❍, 60 ❍, yellow ❍
Also written as 405060YELLOW — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 40 ❍, 50 ❍, 60 ❍, 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 communication with its temperature sensor, meaning it cannot accurately tell how warm your room is and may stop heating your home as a safety precaution. (As reported on Ariston Clas One)
Pick your boiler brand for the 40 ❍, 50 ❍, 60 ❍, yellow ❍ fix
Source
Information for the 40 ❍, 50 ❍, 60 ❍, 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