A car engine needs to be rotating at a significant speed in order for it to start. The starter motor is a powerful electric motor which provides the power to turn the engine. The starter motor works to provide enough power to get the car engine turning at the correct speed for it to start. The starter motor relay basically acts as an ON/OFF voltage control switch, allowing an electric current to flow from the battery to the starter motor. When the ignition key is fully turned or starter button pressed, the power is transmitted via a solenoid switch to the motor.
The starter motor relay will be housed in the relay box, usually found underneath the dashboard. The relay connects to the car's battery, as well as connecting to the specific part that the relay is functioning, in this case the starter motor, via a solenoid switch.
The starter motor relay is made up of a coiled wire which is attached to a strong magnetic base, such as iron, which generates a magnetic field when the electric current flows through it, which either opens or closes the solenoid switch/connection which starts or stops the current to the motor.
Faults can occur with the electrical contacts, relay coil and wiring. The connections can overheat and corrode. Moisture can also seep inside the relay which can compromise the proper functioning of the starter motor relay. It's important when replacing the starter motor relay to buy a part that will be compatible with the make and model of your vehicle. Buying the starter motor relay will guarantee you get the right component that's designed specifically for the make and model of your car.