BoilerFaultCodes 103 High
Boiler Fault Code 103
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 103 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 electronic control system is failing to communicate with an external safety sensor or accessory, causing it to shut down to prevent unsafe operation. (As reported on Main Insul 7)
Pick your boiler brand for the 103 fix
Source
Information for the 103 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