BoilerFaultCodes F86 Medium
Boiler Fault Code F86
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code F86 appears across 1 boiler brand and 8 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 an issue with the connection to your underfloor heating system, which prevents the boiler from communicating correctly with that circuit. (As reported on Heatline Monza)
Pick your boiler brand for the F86 fix
Source
Information for the F86 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