BoilerFaultCodesYour boiler is struggling to switch the flow of heated water between your radiators and your hot water taps because of an internal valve malfunction.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Diverter valve by Grundfos
What causes this fault?
This fault occurs when the internal motor fails to move the valve into the correct position to send heat where it is needed. The most common reason is that the mechanical components inside the valve have become stuck due to a buildup of debris or wear and tear, preventing the motor from completing its cycle. This results in the boiler being unable to differentiate between heating your home and warming your water.
This fault is more frequent during the autumn and winter months when the boiler is regularly switching between heating and hot water demands after a period of summer inactivity.
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 65:3 — 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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