Ford Repair: windstar having trouble starting, diagnostic computer, trouble code

Question
I just bought a 99 windstar last week it has around 74,000 miles. About 2 miles from the dealer the check engine light came on. The van runs great, but one morning after sitting for about 13 hours the battery was totally dead. The theft light wasn't blinking, no lights, radio or anything would work. We jumpstarted it and is has run fine. Yesterday morning after sitting for about 12 hours it hesitated for about 3 seconds and then started and ran fine. This morning after sitting for about 14 hours, the lights work, the radio turns on, but I can't get the van to start. It sounds like it wants to start but to me it seems like the battery is somewhat dead, but not totally. I am almost sure that if I jump it, it will be fine. Any ideas on the problem?
Thanks!

Answer
John, For starters, if that was my vehicle and you just got,, it I would bring it back, and have them repair it for you. Some places in the state have a 30 day warranty on vehicles, expecially used. I would check on this...
2. If your having a check engine light problem you may have, a  sensor/emission problem. The vehicle will probally need to be hooked up to a diagnostic computer, this will give the mechanic a trouble code, and tell him which sensor is bad..
3. You also may have a bad alternator, and battery. Normally, the battery will not hold a charge if the battery is bad. As for the alternator, if it doesnt keep the system charged, your running the vehicle only with the battery..
4. Both the battery and alt can be tested at your local auto zone for free, check with them about this..
I hope this someone helps you,, good luck..