BoilerFaultCodes 9B High
Boiler Fault Code 9B
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 9B appears across 1 boiler brand and 7 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler has lost connection with its internal hot water storage sensor and cannot currently heat your water effectively or safely. (As reported on Viessmann Vitodens 333)
Pick your boiler brand for the 9B fix
Source
Information for the 9B 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