alternator will not charge battery, both tested good, wet pc

I have taken my ford freestar to two different ford dealers and neither one could fix it , tried to sell me a "ford" alternator but if it didn't work they wouldn't take it back. I already put 2 new alternators on it and paid to have the second one checked. It will drain my battery to nothing while I'm driving, I carry an extra battery and booster cables in my van and I installed a voltmeter so I can see when it is charging, If it stops charging I have to stop and restart the van right away or It will need a boost when I do shut it off. I tried to dry out the pcm as ford suggested and I see where it was all covered with silicone by a previous owner. I need a vehicle for my job and this ford is not it. I have a $4000 piece of junk in my yard, I can't sell it , who would want it, won't charge a battery and wont shift into 4th gear, rear windows work sporadically , odometer fades in and out, This van has been a big disappointment to say the least. C'mon ford, this is ridiculous, too many people are complaining about the same thing, you need to start buying these things back!!