High Lockout
NEON2 on Glow-worm Micron 60FF

Your boiler is receiving a request to turn on the heating or hot water, but it has not yet successfully fired the burner.

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

DEMAND ON

What causes this fault?

This fault occurs when the boiler recognizes you want heating or hot water but fails to complete its internal safety checks to ignite the flame. It is usually caused by a mechanical failure in the fan or the air pressure switch, which prevents the boiler from proving it can safely expel exhaust gases. As a result, the system stays in a 'holding' pattern and refuses to fire the burner for safety reasons.

This issue often surfaces during the first cold spell of autumn when a fan that has sat idle all summer struggles to spin up to the required speed.

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 3View →

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