High
Neon 3 lit on Glow-worm Glow-worm Micron 100FF 120FF

Your boiler has detected an issue with its internal airflow system meant to clear exhaust gases, preventing it from safely starting up.

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.

What the manual says

Manufacturer manual

Check if there is 230V~ between 'N/C' on air pressure switch and N. Check yellow cable between printed circuit board and air pressure switch. If satisfactory replace printed circuit board.

From this model's manual
Verified against the Glow Worm Micron 100ff 120ff installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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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