BoilerFaultCodesYour boiler has lost its connection to an internal sensor or controller, meaning it cannot communicate properly to start the heating process.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Defective cable connection.
What causes this fault?
This fault occurs when the boiler's main control board loses the electrical signal from one of its internal components. The most common reason is a loose or damaged wiring connection that prevents the system from confirming it is safe to fire up. It can also be triggered by moisture affecting the plugs or a hardware failure within the printed circuit board itself.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like 8L — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Ideal Maximiser SE is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
Affiliate links — we may earn a commission at no extra cost to you.