Fuel injection system, horns, starter and of course fog lamps, are some of the electrical accessories in the vehicle that use relays for conveying the signal to the related part. A relay works on a principle in which a low current circuit called the control circuit switches or opens a high current circuit called the power circuit. Any defect in the relay will lead to misuse of the component that is linked to the relay. Mostly, relays are fitted in the engine bay and internal fuse or relay containers.