1994 Pontiac Grand Prix 4 cyl Front Wheel Drive Automatic 65,000 miles
I have replaced the alternator and have replaced the battery 3 times in the last 2 months as all of the batteries have tested having dead cells and the car is still not keeping a charge. I will jump it off and drive it and for the next couple of hours it will start but then after 6 hours or so, it won't start and will have to be jumped off again. Could it be that the alternator is actually bad and not the batteries even though it is a new one. Thanks
With everything turned off, use a digital voltmeter across the battery posts. The generic spec for a full charge is 12.6 volts. Start the vehicle, the second reading across the battery posts should be higher than the first, if the charging system is working. You also have to consider alternator wiring circuits and battery wiring also.
Another thought, is something draining the battery, with everything turned off. It's best to check amp draw, usually not close to 1/2 amp draw. An older way to test, is to take battery cable loose, use a testlite between cable and battery post, if lite comes on and stays on, you have a drain. You pull fuses/relays one at a time, when you kill the problem circuit, the lite goes out or amp draw returns to normal. That way you know what circuit the problem is on.