BoilerFaultCodes 1.91 High
Boiler Fault Code 1.91
Also written as 191 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 1.91 appears across 1 boiler brand and 1 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your heating system has encountered a communication error between the main controller and the fan, meaning the unit is unable to start up properly. (As reported on Johnson Starley Aquair S 10)
Pick your boiler brand for the 1.91 fix
Source
Information for the 1.91 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