BoilerFaultCodes F65 High
Boiler Fault Code F65
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code F65 appears across 2 boiler brands and 17 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 boards are having trouble communicating with each other, preventing the system from starting up. (As reported on Glow-worm Ultracom 24cx 30cx)
Pick your boiler brand for the F65 fix
Source
Information for the F65 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