BoilerFaultCodesYour boiler is having trouble communicating with the pump that heats your hot water cylinder, meaning you may experience a lack of 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. It is usually caused by a loose electrical connection, a failing communication module, or the pump itself developing an internal electronic fault that prevents it from responding to the boiler.
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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