BoilerFaultCodes 104 High
Boiler Fault Code 104
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 104 appears across 2 boiler brands and 2 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 communication system is experiencing a fault with an add-on device, causing the system to stop working as a safety precaution. (As reported on Main Insul 7)
Pick your boiler brand for the 104 fix
Source
Information for the 104 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