BoilerFaultCodesYour boiler has detected an issue with the sensor that monitors the temperature of the water returning to the unit, causing it to stop working for safety.
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 Fault
What causes this fault?
This fault occurs when the boiler's control board 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 has physically failed due to age or internal wear, though it can also be caused by loose electrical connections or a fault on the main control board.
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 F5 — 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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