BoilerFaultCodes 129 High
Boiler Fault Code 129
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 129 appears across 2 boiler brands and 4 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler's built-in fan has stopped spinning, which means the system cannot safely clear exhaust gases and has shut down as a precaution. (As reported on Atag iS System)
Pick your boiler brand for the 129 fix
Source
Information for the 129 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 31 August 2026