D.27 Medium
Your boiler's internal control board is having trouble communicating with an external part or accessory, which may prevent the system from starting up correctly.
Technical description: Switching accessory relay 1
Typical repair cost: £180-350 (including labour)
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Protect yourself from future repair bills
A boiler cover plan would cover faults like D.27 — no call-out fees, no surprises.
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Parts commonly replaced
- Printed Circuit Board (PCB)
- Relay Module
- External Wiring Loom
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