BoilerFaultCodesYour boiler has stopped working because it cannot properly measure the temperature of the water coming back from your radiators.
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
What causes this fault?
This fault occurs when the sensor responsible for monitoring the temperature of the water returning to the boiler begins sending incorrect data or fails completely. The most common reason is that the internal components of the sensor have degraded over time, though it can also be caused by loose electrical connections or a build-up of debris on the sensor's surface.
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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