How much does it cost to fix boiler error code Constant RED?

Typical repair cost for the boiler Constant RED fault is £120-250 including labour.

Constant RED High

Boiler Fault Code Constant RED

Also written as CONSTANTRED — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code Constant RED appears across 1 boiler brand and 5 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 that the water inside it is getting too hot and has automatically paused to prevent overheating, but it should restart once it has cooled down sufficiently. (As reported on Grant Vortex Eco)

Pick your boiler brand for the Constant RED fix

Grant Constant RED 5 models

Source

Information for the Constant RED 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