BoilerFaultCodesYour boiler's internal control board is having trouble communicating with an add-on electrical component that manages your external pumps or heating zones.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Switching accessory relay 1
What causes this fault?
This fault occurs when the boiler's brain loses its electrical connection with the internal relay module that controls your external pumps and valves. It is usually caused by a loose wiring connection between these parts or a component failure on one of the circuit boards. Because the boiler can no longer safely coordinate with the rest of your heating system, it stops running to prevent damage.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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A boiler cover plan would cover faults like D.27 — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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