BoilerFaultCodesTechnical description
Return sensor is defective or not properly connected.
What causes this fault?
This fault occurs when the boiler's internal computer loses communication with the sensor that monitors water temperature returning 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 or damaged wiring. Because the boiler cannot accurately track the system temperature, it shuts down as a safety precaution to prevent overheating.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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