Boiler Fault Code C6:75

Also written as C675 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026

Fault code C6:75 appears across 1 boiler brand and 6 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 is getting too hot and has temporarily restricted itself to prevent overheating and ensure safe operation. (As reported on Viessmann Vitodens 333)