I have a 1996 Grand Cherokee Limited this is giving me fits with the charging system. I've replaced the battery twice in the past 3 months. I've also installed a factory rebuilt alternator. I can drive the jeep for weeks at a time and then the battery will be dead. I jump the car and drive it and it runs fine, but if I let it sit over night the battery is dead. I've had charge tests done and the alternator is charging but drops under a load (placed on it by the tester). I've had the battery tested and it shows that the battery is good. Alternator guys tell me the battery is bad, the place where I bought the battery says the alternator is bad. I'm confused. Can someone give me an idea where I can look for a solution to this?

Alternators have a built in regulator that tells them when to turn on and off. Just because the alternator is working, does not mean the regulator is turning it on and off when it should, in turn, over charging or undercharging your battery ruining it. The problem is you could also have a short somewhere that is draining the battery when it gets damp. The starter or a bad battery cable is usually the culprit here. A bad battery cable can mimic a dead battery, and when you jump it you put enough power to allow it to "jump" the bad spot, But also put a major strain on the cars electronics. So start with new cables, a 96 is 15 years old. Inspect the starter for any sign of corrosion or other damage at the same time. If this doesn't help, demand a replacement alternator. 98% of rebuilds are good, but 2% aren't.