Recently my generator light came on and the battery stopped charging. Later the alternator started making noise, and i think it was a bad bering. So last night i put in a new alternator, and it still wouldn't charge. So then I replaced the voltage regulator, and the generator light went out and the battery started charging. Today when i started the car, the generator light came on, and the battery is again not charging (the alternator and voltage regulator were just replaced in sept. 2002 for a similar problem.) What keeps going bad and what is causing it?