High Lockout
Neon 4 NOT lit on Glow-worm Fuelsaver Complheat 40 55

Your boiler is failing to light its pilot light or detect a steady flame, meaning it cannot start the heating process.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Ignition, pilot or flame proving fault.

What causes this fault?

This fault occurs when the boiler attempts to start up but cannot establish or maintain the small pilot flame required to ignite the main burner. The most common reason is a worn-out thermocouple that can no longer sense heat, or a pilot injector that has become blocked with dust and soot over time.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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