If your car is routinely suffering from a dead battery, you may begin to wonder if the problem is the battery itself of the alternator. The alternator is the part of your car responsible for keeping your battery charged. If the alternator is not functioning properly, your car battery will receive a weak charge or no charge at all. You can test the alternator in older model cars using the battery, though it is a somewhat outdated method and not recommended for use on newer model vehicles with sophisticated electronic systems.
Open the hood of your car and locate your battery. Loosen the positive battery terminal slightly with a wrench.
Start your car and allow it to run for a moment.
Reach under the hood and remove the positive cable from the battery, being careful not to let it touch anything while you are removing it. Touching any of the other parts can send up sparks and be dangerous.
If the car dies, your alternator is not working properly. If the car continues to run, your alternator is providing an adequate charge for your car.
Turn car off. Replace and tighten battery cable.
Start your car and allow it to run for a minute.
Turn the headlights on. Observe how bright the headlights are.
Turn the car off, while watching the headlights closely. If they get brighter when you initially turn the car off, chances are good that your alternator was not supplying the car with enough power. If they stay the same or get dimmer, your alternator was providing accurate power.
