HouseCallAuto 4/29/2010It sure sounds like you have a "parasitic draw" from something. Maybe you have a parasitic drain while the vehicle is parked. To verify this, remove the negative battery terminal. Hook up a digital amp meter in between the battery post and the battery terminal. The reading should be no higher than 100 Ma (milliamps) If there is a higher reading it will likely be much higher like 900 Ma. This indicates that something in the vehicle is using power with the key out of the ignition and doors closed. To find the cause usually involves removing every fuse one at a time while watching the meter for a drop to a normal level. Best to start by the underhood fuse panel first because that feed power to the fuse panel inside the car as well. The first fuse to remove should be the fuse that is for the interior lights. The second one should be the radio. Make sure doors remain closed during your fuse removal or you will get a high reading from the interior light. That is why you should remove that one first.
Andy 4/29/2010I agree with the above answer for diagnosis. ...current draw should be no higher than 50 milliamps after 1 hour if the system is correct.