I have a 97 Ford Aerostar that has ran great up until last night. It wouldnt start. I thought it was a dead battery. I jump started it, and it ran fine until i got home. As soon as i turn the engine off, i lose ALL power, even door locks. Like im not even connected to the battery any more?
Anyone? 
The first thing to check are the basics. Slap a voltmeter on the battery to see if it has any charge. (You can get cheap ones if you don’t have one or ask around - someone you know probably does). Check that the battery terminals are clean and tight. Start tracing out the battery cables and checking all of the connections, especially the grounds.
How old is the battery?
If the battery was too weak to start the van yesterday, but you jump started it and drove it, the battery may now be dead.
I suggest checking the connections to the battery, the starter, and the ground connection. I also suggest having someone “load test” the battery. Even if the battery shows 13 or 14 volts it may have enough amperage to turn the engine.
Ill check it in a few. It just didnt seem right that right when i turned the car off, all power was imediatly lost. Not even enough to lock the doors.
Many times I’ve seen batteries fail suddenly and completely. Likely an internal connecting bar has cracked.
You probably aren’t connected to the battery anymore, bad connection. Or the battery is dead.