An alternator is a generator of electric power in your car and is a major component of your vehicle's charging system. Whenever your engine is running, the alternator charges your battery and supplies additional electric power for the vehicle's electrical systems. An alternator is attached to the engine and is driven by a drive belt. The alternator is located in the engine compartment. If the alternator is not working properly, your car will only stay running for as long as the battery has power stored. Once the battery loses power, your car will not start. Normally, a malfunctioning alternator will turn on the battery warning light or will have a low volt gauge reading.