A40 High

Boiler Fault Code A40

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code A40 appears across 2 boiler brands 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 is struggling to move water through the system properly, which is causing it to shut down to prevent overheating. (As reported on Potterton Powermax HE)

Pick your boiler brand for the A40 fix

Ariston A40 2 models Potterton A40 1 model

Source

Information for the A40 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