BoilerFaultCodes A91 High
Boiler Fault Code A91
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code A91 appears across 1 boiler brand and 3 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 temperature is behaving unexpectedly, suggesting a potential circulation issue or a faulty temperature reading. (As reported on Vokera Easi-Heat I)
Pick your boiler brand for the A91 fix
Source
Information for the A91 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 7 July 2026