1. The four horizontal lines in the thermostatic kettle are caused by the failure of the temperature sensor inside the thermostatic kettle. When the temperature sensor fails, the temperature inside the thermostatic kettle will change abnormally, resulting in four horizontal lines on the display screen of the thermostatic kettle.
2. The appearance of four horizontal lines in the thermostatic kettle may also be caused by the failure of the internal circuit board of the thermostatic kettle. When the circuit board fails, the circuit board inside the thermostatic kettle will change abnormally, resulting in four horizontal lines on the display screen of the thermostatic kettle.
3. The appearance of four horizontal lines in the thermostatic kettle may also be caused by the failure of the internal power cord of the thermostatic kettle. When the power cord fails, the power cord inside the thermostat will change abnormally, resulting in four horizontal lines on the display screen of the thermostat.