Boiler Fault Code An 11

Also written as AN11 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026

Fault code An 11 appears across 1 boiler brand and 2 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 light its burner or cannot detect that a flame has been successfully lit, preventing it from heating your water. (As reported on Biasi Advance 25C)