BoilerFaultCodesYour boiler has detected a communication fault with a internal temperature sensor, preventing the system from monitoring the water returning to the unit safely.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Return thermistor open circuit – check/replace connections/thermistor
What causes this fault?
This fault occurs when the boiler's main control board loses touch with the sensor that monitors the temperature of the water coming back from your radiators. The most common reason is that the internal sensor has physically failed or developed a crack, though it can also be caused by a loose or damp connection in the wiring harness.
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 E37 — 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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