BoilerFaultCodesWhat the manual says
Manufacturer manualLow voltage wiring harness error
Shared across the range
This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s manual.
What causes this fault?
This fault occurs when the internal electrical signals between the boiler's control systems and the gas valve are interrupted or lost. The most common reason is a loose connection in the wiring or a degradation of the copper pins within the harness, which prevents the computer from safely controlling the boiler's operation.
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 →
Boiler cover options
Avoid the next call-out bill
A cover plan would handle faults like ON ON ON: no call-out fees, no surprise bills.
Approved partner
Get a quote →
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Affiliate links. We may earn a commission at no extra cost to you.