Solenoid switch
If the starter does not work, the reasons may be a discharged battery, an open circuit in the starter power supply, or a breakdown of the starter itself.
One of the first places in the list of the last is the failure of the electromagnetic switch, which is very important 
role in the starter start process. When the key in the ignition lock is turned to the extreme position, current flows through the windings of the electromagnet installed on the starter of the electromagnetic switch, and the generated magnetic field moves the core, which, with the help of a lever, moves the gear along the rotor shaft and engages with the flywheel ring gear. When the gear is fully engaged with the flywheel rim, the core of the electromagnet closes the main contacts of the starter and drives it. This principle of operation of the electromagnetic circuit breaker leads to two typical failures.
The first concerns damage to the winding of the circuit breaker electromagnets. This is manifested by the absence of any reaction from the starter when it is turned on. The second reason is the thermoelectric processes that accompany the closing and opening of contacts, especially those through which, as in the starter, a current flows with great force. Harmful discharges in the form of sparks occur on the contacts. They cause pitting and risers. The contact surfaces gradually lose contact until, finally, they completely cease to conduct current. If this happens, the core of the electromagnet making such contacts will not cause current to flow. In this case, after turning the key in the ignition switch to the extreme position, only a single click of the meshing gear with the flywheel rim will be heard.
Replacing a damaged solenoid switch usually requires the removal of the entire starter, and sometimes its partial disassembly. It happens that the replacement operation can be performed on the car without removing the starter. In a situation where a contact has failed in a non-standard switch and, moreover, there is neither an original nor substitutes on the market, it remains only to disassemble the switch housing, grind the contacts and assemble them as a whole.
