c/u/ High

Boiler Fault Code c/u/

Also written as CU — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code c/u/ 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 system is experiencing an electrical connection issue, causing it to stop operating correctly to protect itself. (As reported on Worcester Bosch GB162)

Pick your boiler brand for the c/u/ fix

Worcester Bosch c/u/ 1 model

Source

Information for the c/u/ 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 7 July 2026