BoilerFaultCodesYour boiler is having trouble communicating with the pump that heats your hot water cylinder, meaning you might not have hot water.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Cylinder charging pump via accessory module
What causes this fault?
This fault occurs when the boiler's main control board loses its connection with the external pump responsible for heating your hot water tank. The most common reason is an electrical communication failure within the plug-in module or a physical fault with the pump itself, preventing the system from diverting heat to your water cylinder.
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 D.12 — 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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