Chrysler Repair: Battery dies in about 1 hour, jeep grand cherokee, jeep line

Question
I have a 2000 Jeep Grand Cherokee.  It has been sitting idle for about 3 months.  It would not turn over when I tried to start it.  I put the battery on a charger and let it reach "fully charged", one evening.  I cranked and fired right up and ran well.  The next morning it would not crank.  I recharged the battery to full and the car started easily.  I waited one hour and tried again and there was not enough power to crank the engine.  I cleaned the battery posts and cable clamps before charging.

Answer
Hi Ray,
Assuming that the battery will hold a charge, then there must be a component that is drawing a lot of current even with the ignition off. You might verify the battery by disconnecting it (right after fully charging it) and the reconnecting an hour later to see if it is self-draining/discharging. If that proves to be ok then I would suggest that you consider whether there may be hidden light bulb 'on' somewhere, although that wouldn't in the usual circumstances discharge a battery so quickly.
Do you have a volt-ohm-ammeter? If so you could put the meter in series with the - post clamp and the -post of the battery and see what the 'ignition off draw' current is registering. It should be below 100 milliamp, although for about 30 minutes it might be as high as 500 mA while the various control modules turn themselves off. If it is way over that, which it would have to be to discharge the battery so quickly, then you have to consider what could be powered even though the igntion is off. This is usually the courtesy lights, the body computer, the door lock circuits, the vehicle theft circuits.
I don't have any wiring diagrams for the Jeep line earlier than 2004 so that really limits my ability to tell you how to disconnect these circuits and watch for changes in the current draw. But that is basically the idea. There is an ignition off draw fuse that powers all these devices so if you can identify which # fuse that is I would start there by pulling it to see if that is what is shorting out the battery, or not. But without a wiring diagram I can't suggest exactly where to begin disconnecting things, but probably pulling the plugs on the body control module, and searching for any hidden bulbs/radio amplifier/courtesy devices that might be 'on' when you don't expect them to be ia my best suggestion.