BoilerFaultCodes con High
Boiler Fault Code con
Also written as CON — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code con appears across 1 boiler brand and 25 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 screen and main control board are having trouble talking to each other, meaning the unit cannot function. (As reported on Vaillant ecoTEC)
Pick your boiler brand for the con fix
Source
Information for the con 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