High
Mains fuse F2 on PCB 40 blown on Ideal Response

Your boiler has lost power because an internal fuse has blown, likely caused by an electrical fault in the pump.

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 pump for shorts between L/N and L/E. Disconnect pump and lead to PCB 41, renew fuse and reconnect to determine faulty item.

From this model's manual
Verified against the Ideal Response 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 an electrical component within the boiler draws too much current, causing a safety fuse on the control board to blow and cut all power. The most common reason is that the central heating pump has developed an internal short circuit or has seized, often due to a build-up of debris or water leaking into its electrical housing.

This issue is most frequent at the start of autumn when the heating is turned on for the first time after summer, as the pump is prone to seizing after long periods of inactivity.

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 Mains fuse F2 on PCB 40 blown: 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