Solenoid switch refers to the control switch on the automobile starter, which is one of the three major parts of the starter (DC motor, transmission meshing mechanism and electromagnetic switch). Its working principle is that the coil generates electromagnetic suction after being electrified, which makes the movable iron core move. On the one hand, it pulls the transmission meshing mechanism to make the starter pinion move forward and mesh with the flywheel ring gear of the engine, On the other hand, push the switch contact to make the DC motor power on, so as to drive the engine to start.