Boiler Fault Code A 01

Also written as A01 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026

Fault code A 01 appears across 3 boiler brands and 6 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has failed to light because it cannot detect a flame, meaning you currently have no heating or hot water. (As reported on Vokera Verve I 50)