A2 High

Boiler Fault Code A2

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code A2 appears across 3 boiler brands and 15 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has sensed that the internal pump is malfunctioning or water is not circulating correctly, which has caused the system to stop as a safety precaution. (As reported on Viessmann Vitodens 200)

Pick your boiler brand for the A2 fix

Atag A2 2 models Viessmann A2 12 models Worcester Bosch A2 1 model

Source

Information for the A2 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