BoilerFaultCodesYour boiler has switched itself off because it has detected it is getting too hot, likely due to a blockage or a pump that isn't circulating water properly.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Heat exchanger blockage or pump fault (Overheat)
What causes this fault?
This fault occurs because the internal sensors have detected that the water inside the boiler is reaching a dangerously high temperature. It is usually caused by a pump failure that prevents water from moving away from the burner, or a build-up of debris that has physically blocked the heat exchanger. Because the heat cannot be carried away to your radiators or taps, the boiler shuts down to prevent internal damage.
This issue often surfaces when you first turn your heating back on in autumn, as pumps can seize up after being idle during the summer months.
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 F3 — no call-out fees, no surprises.
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