BoilerFaultCodes AA9977 High
Boiler Fault Code AA9977
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code AA9977 appears across 1 boiler brand 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 internal computer is experiencing a communication error and cannot properly monitor its own safety systems. (As reported on Ariston E-Combi One 30)
Pick your boiler brand for the AA9977 fix
Source
Information for the AA9977 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