Many modern cars are fit with a warning light that appears as "ALT" or in the shape of a battery; This occurs when the alternator begins to fail. If the battery is fully charged and the car still does not start, this is an indication of potential alternator failure. If a car does not have an alternator warning light, the lights on the dashboard and throughout the interior will dim. Power windows and power locks work more slowly than usual when the alternator begins to fail.
A visual check underneath the hood of the car can reveal loose wire or a faulty connection. Seek the opinion of a professional in order to be certain that the alternator is the faulty equipment. The alternator controls all of the electrical currents in your vehicle, so a car is not drivable without a functioning alternator.