Your boiler has detected that a temperature sensor is not correctly attached to the internal pipework, preventing it from monitoring heat levels safely.

Mounting fault sensor S0

What causes this fault?

This fault occurs when the boiler's control system loses contact with a temperature sensor that should be firmly clipped to the internal pipework. The most common reason is that the metal spring clip holding the sensor has become loose or displaced, often due to natural vibrations or heat expansion over time. Because the boiler can no longer accurately measure how hot the water is getting, it shuts down as a safety precaution to prevent overheating.