BoilerFaultCodesYour boiler has stopped working because it cannot correctly 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 sensor fault
What causes this fault?
This fault occurs when the boiler's control board loses communication with the sensor that monitors water returning from your heating system. The most common reason is that the internal sensor has developed a chemical failure or electrical short, preventing the boiler from knowing if it is safe to continue firing. In some cases, it can also be caused by loose or damaged wiring connecting that sensor to the main computer.
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 AL73 — no call-out fees, no surprises.
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