Why cant I change from vent to defrost

Hey Chris. Your A/C ducts in your dash are controlled by little doors that direct the air flow. On modern cars the actuators that control the doors are electric motors. Older cars are vacuum controlled, but I believe yours are controlled with cables. You’ll need to take apart your dashboard and inspect the cable and the blend door itself. It sounds like your cable is binding up. If you can get in there and get some pictures, post them here and I can guide you further.

I don’t remember how the AC is controlled, but I used to have a 98 Dodge Neon R/T and removing the AC controls is very easy to do. Replacing it is also just as easy if you can find a replacement set of controls in a junk yard. You need to see how they are operated first to determine if they are controlled by cables or electric.