BoilerFaultCodesTechnical description
Return thermistor fault
What causes this fault?
This fault occurs when the boiler's internal computer receives an incorrect or missing signal from the sensor that monitors water temperature coming back from your radiators. The most common reason is that the sensor itself has worn out or developed a spiritual electrical fault, though it can also be triggered by loose or damaged wiring between the sensor and the main control board.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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