I have a 1998 ford windstar 3.0L. it started sputtering and i thought it was out of gas i got gas and then wo start it ent to start it and it was dead. i got a jump and it ran for a few minutes and died again. i switched the battery from my other car into the ford and it started up ran for a little and shut off again. when i went it, it was dead again i know it isnt the battery i think it might be the alternator. what do you think?

You can check the charge on the batteries that you have had to replace. If they are well under 10V you probably have a bad alternator. The battery is only used to supply initial power to the car so once that battery is used up then they car may die. If you can get the van running you can hook up a volt meter to to the battery terminals and see if you are getting more than 12volts, ideal is 14, if you aren't getting above 12 then it's pretty sure-fire that it's the alternator. It really sounds to me like you should get that alternator checked out, and maybe you can find someone who can do a deep charge on one of those batteries so you can use it instead of buying a new one.

An easy check to tell if it is the battery or alternator, is to remove the ground terminal from the battery while the engine is running, if the engine dies it is the alternatot