9F High

Boiler Fault Code 9F

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code 9F appears across 3 boiler brands and 9 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler's internal computer is having trouble measuring its own temperature, which prevents it from operating safely. (As reported on Ideal Maximiser SE)

Pick your boiler brand for the 9F fix

Ideal 9F 1 model Viessmann 9F 7 models Worcester Bosch 9F 1 model

Source

Information for the 9F 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