Boiler Fault Code (B) LED turning on

Also written as BLEDTURNINGON — same fault.

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

Fault code (B) LED turning on appears across 1 boiler brand 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 has tried to ignite to provide heat but failed to detect a flame, causing the system to shut down for safety. (As reported on Ariston Genus 24 RFFI)