neon4 High

Glow-worm neon4 Fault Code

Also written as NEON4 — same fault.

The Glow-worm neon4 fault code means: your boiler is unable to light the pilot flame, which means it cannot fire up to provide heating or hot water.. It appears on 12 Glow-worm models in our database.

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: Is there 240V~ between pilot gas valve solenoid blue and brown connections? Isolate supply, test harness continuity. If satisfactory replace printed circuit board.

What causes the Glow-worm neon4 fault?

This fault occurs when the boiler's control system attempts to light the pilot flame but fails to receive the electrical signal or gas flow required to start the ignition process. The most common reason is an electrical failure in the main circuit board or a faulty solenoid preventing the gas valve from opening, meaning the boiler cannot safely begin the heating process.

Typical repair cost £180-350 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Glow-worm models that show the neon4 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Glow-worm neon4 fault code information on this page is sourced and cross-checked against the official Glow-worm service / installation manuals for each affected model.

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