High Lockout
Neon 4 lit (No) on Glow-worm Ultimate3

Your boiler is failing to light the gas flame or cannot detect that the flame has started, so it has shut down for safety.

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 tries to start but fails to either generate a spark or open the gas flow to create a flame. The most common reasons are a worn-out ignition electrode that can no longer create a spark or a faulty gas valve that isn't letting fuel into the burner.

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.

Find a Gas Safe engineer
Search the official register →

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