High Lockout
neon3 on Glow-worm Space Saver

Your boiler has detected an internal electrical communication error, meaning it cannot safely confirm the fan is working to clear waste gases.

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

Is there 240V~ between 1 on air pressure switch and 10? Check yellow cable between printed circuit board and air pressure switch. If satisfactory replace printed circuit board.

What causes this fault?

This fault occurs when the boiler's main control board loses electrical contact with the safety sensors that monitor the air flow. The most common reason is a physical break or loose connection in the wiring, or a component failure on the circuit board itself that prevents it from reading the fan's status. Essentially, the boiler's 'brain' can no longer talk to its 'lungs,' so it shuts down for safety.

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 2View →

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