Your boiler has lost communication with its internal temperature sensor, meaning it cannot monitor heat levels and has shut down as a safety precaution.

No signal from the temperature sensor at the heating block available – replace the temperature sensor, the connecting lead or the control unit

What causes this fault?

This fault occurs when the boiler's brain can no longer detect a signal from the sensor that monitors the heat of the water. The most common reason is that the sensor has physically failed or a wire has come loose, causing the boiler to shut down immediately to prevent overheating. In some cases, a fault within the main control board means it can no longer 'hear' the messages being sent by the sensor.