BoilerFaultCodes 0A3 High
Boiler Fault Code 0A3
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 0A3 appears across 1 boiler brand and 3 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler has switched itself off because it has detected dangerously high temperatures, likely caused by a disruption in the flow of water circulating through your radiators. (As reported on Alpha Pro Tec Plus)
Pick your boiler brand for the 0A3 fix
Source
Information for the 0A3 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