BoilerFaultCodesYour boiler has sensed that parts of the system have become too hot and has shut itself down as a safety precaution.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Overheat Thermostat
What causes this fault?
This fault occurs when the internal water temperature exceeds safe limits, triggering a safety sensor to cut the power. The most common reasons are a failed water pump that isn't moving heat away from the boiler quickly enough, or a build-up of debris and sludge that is restricting the flow within the main heat exchanger.
This fault is more frequent when the heating is first turned on after summer, as pump components can seize during long periods of inactivity.
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 E83485 — no call-out fees, no surprises.
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