First hook up a voltmeter to the battery, start the car, needs should read 13.8-15 volts, if not the alt needs to be replaced, testing is done with a fully charged battery!
Also: You may have a parasitic drain test this way:
Get an analog voltmeter remove the negative battery cable, attach the Black lead to the battery post, Red lead to cable end, then pull fuses one at a time, make sure there are no accessories or lights in the on position, Key off! Close the door after each fuse and check meter, when you pull the fuse for the bad curcuit, the meter will drop to 1 volt or so. Check all fuses, even under the hood. If meter does not drop, remove the battery connection from the alternator, if it drops now, the diodes are bad in the alternator. Put the fuse back in were it goes as you go so you don't forget which fuse goes were!
Sunday, July 11th, 2010 AT 8:33 AM