D.12 High
Your boiler is having trouble communicating with the pump that heats your hot water cylinder, meaning you may experience a lack of hot water.
Technical description: Cylinder charging pump via accessory module
Typical repair cost: £150-£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.12 — no call-out fees, no surprises.
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Parts commonly replaced
- Accessory module
- Cylinder charging pump
- Wiring harness
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