Your boiler has detected a technical fault with the sensor that monitors water returning to the unit, causing the system to shut down as a safety precaution.

Temp.sensor fault: Short-circuit in return temperature sensor.

What causes this fault?

This fault occurs when the boiler’s internal computer receives an incorrect electrical signal from the sensor that monitors water coming back from your radiators. The most common reason is that the sensor has developed an internal electrical short or the protective coating on the connecting wires has worn away, causing the system to shut down for safety. In some cases, water ingress or moisture near the electrical connections can also trigger this specific error.