Emergency
Neon 3 on Glow-worm Glow-worm Micron 100FF 120FF

Your boiler is failing to clear combustion gases properly, so it has safely shut itself down to prevent carbon monoxide buildup.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

What the manual says

Manufacturer manual

Air flow proving fault - that is fan or air pressure switch

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 emergency 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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