Some of the electrical accessories in the car the fuel injection system,
Horns, starter and fog lamps utilize relays to relay the electrical signals to the concerned part. A relay works by having a control circuit, a low current in this case, to switch on or off a power circuit which is high current. If we have a defective relay, the associated component will not operate as it is suppose to or not at all. As a rule, relays are installed in the engine compartment and in interior fuse and relay boxes.