I have a 99 dodge caravan. I moved from tx to wv. before i left i had the thermostat replaced. driving 1600 miles with no problem.
Now the van will heat up but I dont get any heat and the check engine light will go on and off. There is some noise also, sounds like it's coming from behind the dash, like somthing is trying to open and close. A few times it started to overheat and when I pulled over and put it in park it went back to normal. I thought it might be the water heater. Does anybody have any ideas of what it might be?

thanks

 

I would start with the check engine light, it might be related to your heat problems. The caravan has a heating and A/C self diagnostic program you can run that will display any issues with the HVAC unit itself but it sounds as if your problem is coolent flow.
Does it have rear heat or A/C?

 

no, it doesnt have rear heat or air

 

The sounds behind the dash are the doors in the HVAC box opening and closing, but the overheating is the more serious issue here. Make sure the coolent system is full and that you have coolent flow. Check the upper and lower radiator hoses and both hoses to the heater core and make sure they are hot with the engine at operating temp and the heat on high. The 3.3 and 3.8 motors have had issues with the water pumps.

 

the water pump and hoses are fine but the door on the hvac unit opens and closes only at high revs. is there a circut for that?

 

Could be the new thermostat is bad. Some of the cheaper ones on the market are prone to fast failure.