In the vehicle several electrical accessories like the fuel injection system,
Horns, starter fog lamps among others use relay to switch electrical signals to the component in the car. Relays function through the employment of a low current circuit, called the controlling circuit, to establish or interrupt a high current circuit, that is, the controlled circuit. If relay is defective its operation concerning the concerned component will not be normal. Usually, relays are installed in the hood and in the compartments within the cabin with fuses and relays.