Boiler Fault Code Neon L4

Also written as NEONL4 — same fault.

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

Fault code Neon L4 appears across 1 boiler brand and 1 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler is failing to detect a flame, so it has purposefully shut itself down to prevent a gas leak. (As reported on Halstead Hero)