This is because there is an automatic return device installed inside, some are controlled by the wiper intermittent device, and some are inside the wiper motor! The interrupter is controlled because there is a relay in it! At the moment of closing, the relay is still energized, so the motor continues to work! When the wiper returns to the bottom, the contact on the internal gear of the wiper motor is disconnected, which means that the relay is cut off! So it will automatically shut down! The principle is that the copper sheet on the surface of the rotating gear inside the wiper motor contacts, and the power supply is connected and disconnected through it!