New batery dead next day ford expedition

Make sure your charging system works ok. With everything off check battery amp draw, I use 50 ma as a base, it might be a little more. 50 ma is .050 amp not even a tenth of an amp. Make sure no lights on anywhere, interior--under the hood, wherever. Best time to check that is in the dark. Sometimes a faulty generator may let the battery drain. Other wise pull/ replace fuses one at a time, when you pull the fuse on the problem circuit, the drain returns to normal.

Sounds like a bad alternator to me..

Sounds like a short or draw. Start by checking glove compartment light, under hood light, and ensure all other switches/lights are off. Also, it's common for the rear wiper to draw power. Try unplugging rear wiper. You can pull the fuse but it does multiple things. Fuse #14 in the passenger compartment (15A-Blue). Lastly, it could be the GEM. Lots of people have had issues with their GEM getting wet.

I've posted the same response on your other question. (Assuming you're talking about your 1999 Expedition)

Hey MGM_Mobile Electronics. What is the GEM??? I have a 1999 Ford Expedition and the running board lights dont turn off when the rear hatch is open and the battery dies. Got any suggestions? THanks Bill

GEM stands for "General/Generic Electric Module." Basically, the GEM controls the interior lights, exterior courtesy lights and accessory power as well. When you leave the rear hatch open, the lights stay on? Do your interior lights stay on when this happens? The lights usually stay on because they think a door is ajar. Basically, a door switch gets stuck open or the sensor fails. You can try spraying WD-40 or some other lubricant in the latch. See if you can get the lights to turn off with all the doors closed, including the rear hatch.