Your boiler has detected a communication error with its internal control system or a connected sensor, which might cause it to operate incorrectly or stop working.

Without time delay

What causes this fault?

This fault occurs when the boiler's central brain loses contact with the sensors that monitor heat levels, often due to a broken internal wire or a sensor that has failed completely. Because the control system can no longer safely tell how hot the water is, it shuts down to prevent the system from overheating. It is usually caused by a physical break in the electrical circuit or moisture damage to the sensitive electronic connections.