BoilerFaultCodes -9OC High
Boiler Fault Code -9OC
Also written as 9OC — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code -9OC 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 a problem with the sensor that monitors hot water temperature, likely due to a loose connection or a fault in the internal wiring. (As reported on Glow-worm Ultracom 24cx 30cx)
Pick your boiler brand for the -9OC fix
Source
Information for the -9OC 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