High Lockout
Neon4 on Glow-worm Fuelsaver Complheat 40 55

Your boiler is attempting to start but cannot light or maintain the flame needed to provide heating and hot water.

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's internal safety system fails to detect a steady flame after several attempts to light. The most common reasons are a blocked pilot light burner or a worn-out sensor that can no longer tell the control board that the gas has successfully ignited.

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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Related fault codes

Neon 1View →Neon 2View →

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