i have a 1994 aerostaR v 6 3.0 i noticed when im driving the temp is fine but when i stop it starts getting really hot (at idle) no leaks that i can see anywhere . so i changed the thermostat still the same also the heater controls are not working it only works on defrost no vents it has vaccuum controls. after i put the new thermostat in i was not able to get any heat inside the vehicle just cold air . and yes im sure i put the thermostat in the right way . any suggestions other than that this van has been a great runner

approach solving the problem in a systematic manner, or take it to a shop you can trust. random guesses from people thousands of miles away aren't going to fix this because it will come down to a question:answer thing.

Check the rubber gasket on the cap for cracks, gunk, etc - that's usually the pressure loss point without noticeable steam to clue you in and since low circulation at idle it would account for a pressure leak being the cap gasket. A wild assed guess would also be a bad impeller (worn off blades but still working enough that circulation is ok at driving speeds) in the water pump. If you pull the hose to it you can see the general condition of the impeller with a flashlight and inspection mirror without removal.   Could also be a clogging but not clogged radiator - the thin tubes could be building up internal deposits.        

You've probably got an unhooked vaccuum hose under the hood that leads to the heater controls under the dash.  Find it and fix it, and you'll likely get your heater selections back.   As far as the 'no heat' issue from the heater.  You probably need to burp/purge the air out of the heater core.  Aerostar's are notorious for having problems where they don't flow water through the heater core, and it's usually an air blockage.   Preston