BoilerFaultCodesYour boiler has stopped working because it cannot properly measure the temperature of the water returning 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 fault
What causes this fault?
This fault occurs when the boiler's control board loses communication with the sensor that monitors the temperature of the water coming back from your heating system. The most common reason is that the sensor itself has suffered an internal electrical failure, though it can also be caused by loose wiring or a damp connection inside the boiler.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
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A boiler cover plan would cover faults like L5 — 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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