Your boiler has stopped working because a sensor that monitors water temperature has lost its connection or stopped sending a signal.

Return NTC: NTCbroken; NTCcable broken; Defective connection at NTC Defective connection at electronics | Return-NTC cable defective/broken NTC faulty

What causes this fault?

This fault occurs when the boiler's main control board loses communication with the sensor that monitors the temperature of the water leaving the unit. The most common reasons are an electrical failure within the sensor itself or a break in the wiring caused by vibration, heat exposure, or moisture. Without this data, the boiler shuts down as a safety precaution to prevent overheating.