BoilerFaultCodesYour boiler is having trouble 'talking' to its internal pump, which means it cannot flow water around the system to heat your home.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Installation accessories- Communication with variable speed pump (low voltage HM)
What causes this fault?
This fault occurs when the boiler's main control board loses its digital connection with the internal circulation pump. The most common reason is a hardware failure within the pump’s electronic motor head or a loose communication cable, meaning the boiler can no longer control the speed of the water flow. Without this connection, the system shuts down as a safety precaution to prevent the heat exchanger from overheating.
This fault is more common in autumn when the boiler is switched back on after being idle all summer, which can cause internal pump components to seize or fail.
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 A9 — no call-out fees, no surprises.
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