BoilerFaultCodesYour boiler has detected a problem with the sensor that monitors the temperature of the water coming back from your radiators, preventing it from heating correctly.
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 thermistor fault
What causes this fault?
This fault occurs when the control board loses communication with the sensor that monitors the temperature of water returning to the boiler. The most common reason is that the sensor has physically failed due to wear and tear, or the electrical connection has become loose or corroded. Without this data, the boiler shuts down to prevent itself from overheating or burning fuel inefficiently.
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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