My car is blowing hot air out on an irregular schedule. When I first turn the car on and turn the top middle and bottom vents on (along with the AC button) the face vents blow decently cold air while the top and bottom vents blow warm air. As I start to drive and especially when I get on a parkway/highway (70+ mph) the top and bottom vents begin to blast extremely hot air and the face vents turn to luke warm. When I turn the top and bottom vents off to keep the hot air from coming out it just comes out of the face vents. I have added refrigerant recently and also replaced the blower resistor final stage unit. Any help is appreciated!!