I have a '98 Expy that wouldn't start about 3 weeks ago. I took out the battery (which was under warranty) and had it replaced. The expy then started fine and ran for a week.
Then I had the same problem(wouldn't start). I took the battery out, charged it and the vehicle started right up. About a week later, it wouldn't start again.
NOT SOLVED YET.
I took all to 2 different parts shops yesterday to have the alternator & battery tested. Both checked OK at both locations. The alternator is generating 14.2 volts at idle. As I stopped on my way home, as luck would have it, the battery wouldn't start the expy again. Well, I bought a spare battery, put it in and I got home.
THIS IS WHERE I AM NOW.
The belt tension seems fine. Wondering if the STARTER could be my problem. The battery connections look OK.
Note* After the battery won't start the vehicle it seems as if I hear a brief clicking coming from an area near my fuse box.
I read through a lot of posts in this forum and am going to use a meter to see if there is an electrical drain somewhere, but I have not installed any aftermarket products (such as CD or subs). The Expedition has never died or shown dim lights while the engine was running. Logic tells me that something must be draining the battery, but who knows.
Any thoughts or ideas would be much appreciated.

 

Did they test the alternator under load? Is it putting out less voltage at higher RPM?

As you said, testing with a meter is needed. A post I saw yesterday mentioned (I believe) having someone watch the meter between your disconnected negative battery cable and the negative battery terminal. With the truck off, and the doors closed it should be draining a minute amount (clock, etc.). If it's high, pull fuses one-by-one until it drops to normal, then start your search with whatever that fuse is for.

There's a recent post about someone finding the light under the hood staying on unbeknownst to anyone, and another post about the rear dome lamp being set to the on position.

 

Hello, new member here. ! have the same problem with my 01 Expy EB. Drives me crazy. I have to disconnect the battery whenever out of town for more than 2 days.

There are at least 2 additional contributing annoyances, maybe someone out there can provide workarounds or solutions to them:

1 - leaving the doors ajar is not a good thing because the interior and running board lights do not automatically shut off. Result: dead battery overnight.

2 - the cigarette lighter and 12v accessory plugs are both unswitched, so they remain live even with the key in the off position. Result: dead battery overnight if I leave my cell phone adapter plugged in, even with no phone attached.

I will be trying to trace the leak in the coming days. I'll report what, if anything, I find.

Cheers.

 

14.2V at idle seems higher than what would be ideal. I've always thought that 13.7-14.2V at 2000RPM is the ideal output.

Maybe it's going the other way and the alternator is cooking your battery.

 

I held up the white flag and surrendered. Took it to a shop. I am suspecting the starter, but I just don't have the patience to deal with it. I tried the volt meter [BTW, Disconnect the positive terminal...red meter wire to the(disconnected) red cable / black meter wire to the (connected) black cable. I blew fuses on my meter connecting the other way. I still didn't get a good reading...it said 1 on the 200ma setting.
Anyway, as it is fixed, I will post results. I appreciate the benefit and purpose of these forums.

 

Solution..............
OK, I got a call from the shop telling me that the positive cable connector had a crack in it. About $20 parts, labor & diagnosis. Makes sense! If I dont post after a week or two, you shall assume this was the 'whole' problem.