BoilerFaultCodes C6 High
Boiler Fault Code C6
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code C6 appears across 2 boiler brands and 50 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 internal exhaust fan is spinning faster than it should, so it has shut down as a safety precaution to prevent incorrect combustion. (As reported on Worcester Bosch ZWB 7-25)
Pick your boiler brand for the C6 fix
Source
Information for the C6 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