High
Fan Hunt on Glow-worm Ultimate

Your boiler is struggling to start up properly because the main internal computer is failing to control the fan correctly.

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

Faulty printed circuit board

From this model's manual
Verified against the Glow Worm Ultimate System 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.

What causes this fault?

This fault occurs when the boiler's main control board loses the ability to communicate properly with the fan motor, leading to erratic speeds or 'hunting' for the correct setting. The most common reason is that the electrical components on the circuit board have degraded over time, meaning it can no longer send a steady signal to keep the fan running safely.

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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