High
neon 1 not lit on Glow-worm Ultimate3 Combi

Your boiler is not receiving electrical power or has an internal blown fuse, meaning it cannot start the ignition process.

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

Fault with mains supply or PCB fuse

From this model's manual
Verified against the Ultimate 50 Ff 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 electrical circuit required to wake up the boiler is broken, preventing the control board from receiving power. The most common reason is a blown fuse within the boiler or at the wall switch, often caused by a sudden electrical surge or a faulty internal component like a failing pump or fan. If the fuses are intact, it typically indicates that the main printed circuit board has suffered an electrical failure and can no longer process commands.

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.

Find a Gas Safe engineer
Search the official register →

Avoid the next call-out bill

A cover plan would handle faults like neon 1 not lit: no call-out fees, no surprise bills.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

Related guides you might find useful