Your boiler has lost its connection with the thermostat or control panel, meaning it cannot receive instructions to turn on or off.

Loss of communication with external control (Alpha Climatic)

What causes this fault?

This fault occurs when the boiler and your thermostat can no longer 'talk' to each other, often due to physical interference or a hardware failure. The most common reason is that the batteries in your room thermostat have died or the wireless receiver attached to the boiler has lost its signal. In some cases, it may be caused by a faulty circuit board that is unable to process incoming signals from your controls.