BoilerFaultCodesYour boiler has detected an issue with the sensor that monitors the temperature of the water coming back from your radiators, preventing the system from running efficiently or at all.
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 boiler's control board receives an impossible 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 shifted out of its calibrated range, though it can also be caused by loose or damaged internal wiring. Because the boiler no longer knows the exact temperature of the water, it shuts down to prevent potentially overheating the heat exchanger.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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