BoilerFaultCodesYour boiler has detected an issue with the sensor that monitors the temperature of the water returning from your radiators.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Central heating return negative temperature coefficient (NTC) thermostat fault.
What causes this fault?
This fault occurs when the boiler's internal computer receives an illogical or missing signal from the sensor that monitors water returning from your radiators. The most common reason is that the sensor has physically failed or developed a chemical build-up, but it can also be caused by damaged internal wiring or a loose connection.
This fault is more common when the heating is first turned on after summer, as the sudden change in temperature can cause aging sensors to 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 E40 — 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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