How much does it cost to fix boiler error code 4 / Y?

Typical repair cost for the boiler 4 / Y fault is £120-220 including labour.

4 / Y High

Boiler Fault Code 4 / Y

Also written as 4Y — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code 4 / Y 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's temperature-sensing component is not registering a signal, meaning the system has stopped operating to prevent overheating. (As reported on Ideal Maximiser SE)

Pick your boiler brand for the 4 / Y fix

Ideal 4 / Y 1 model

Source

Information for the 4 / Y 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