BoilerFaultCodesYour boiler has detected a problem with the sensor that monitors the temperature of the water coming back into the unit, causing it to shut down 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 impossible or inconsistent reading from the sensor that monitors water returning from your radiators. The most common reason is that the sensor has physically failed or developed a short circuit, but it can also be triggered by damaged internal wiring or a fault with the main circuit 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 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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