BoilerFaultCodesYour boiler has lost its safety connection to an external controller or a safety link is missing, causing the system to stop working for protection.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Jumper 8-9 not detected.
What causes this fault?
This fault occurs when the electrical connection between two specific terminals on the control board is broken, acting like a safety trip switch that stops the boiler from running. It is often caused by a loose connection in the external thermostat wiring or because a small metal link wire, which completes the circuit, has come loose or been removed. In some cases, it can indicate that the main control board has developed a fault and can no longer detect this vital safety loop.
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.
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A boiler cover plan would cover faults like d3 — no call-out fees, no surprises.
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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.
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