I have a 2003 dodge caravan se. I got up one morning to take the kids to school and noticed that the heat was not working. I thought at first that it was a radiator problem, but I soon realize that I had heat as long as I turned the fan **** on the dash all the way to the highest level. When I did that, then the fans in the dash started blowing on high and I had heat. But none of the lower fan settings work at all. It appears to go from being off ( any setting below high) to high. On high the fans are very loud and the heat intense. I have to keep turning it on and off. It was working fine the night before. What could it be?

 

It is probably just a blower resistor
cheap part and easy to fix(at least on my jeep)

did the same as you say, works only on high, cool air only works on high too?

others will post where it is on your van, probably behind the glove box

 

I check on my 06 it is behind the glove box here is a pic, to open the glove box there are 2 tabs to press on the inside of the box that after pressing them it allows the box to swing open all the way, then there are just 2 screws that hold the resistor in, and (probably a red tab on the connector that you have to slide to the side)


And Make sure to pull your Neg battery cable before starting, just incase

 

and if the motor is noisy, you probably need the blower motor also.