Many parts of your car work off power from the battery. These car parts, like the fuel pump and the electric cooling fan, take voltage from the battery through the use of relays. A relay ensures that power flow from the battery comes in small, easily controllable doses, to prevent any fire hazards from developing in your car's engine bay. Without relays, you wouldn't be able to control the amount of power that moves from the battery. Being able to regulate the battery's power flow is useful for instances when you want to hook up additional electrical components to your car's circuits. Using a relay would ensure that the electrical component receives just the amount it needs, protecting the component's wiring from overloading. More simply, relays are also used to connect your car's electric components to a power source. A defective relay often makes itself known immediately. If the headlights' relays don't work properly, for example, you wouldn't be able to activate the headlights. When that happens, check on the connections for corrosion. Corroded connections are the most common cause of relay failure, and, unfortunately, the only solution is replacement. Check out our catalogs at Car Stuff to choose from the many relays we have.