When I first start my truck AC works fine. After time the pressure of air gradually goes down coming from vents and fan air gets louder as fan is still blowing but not coming out of the vents very hard. I can turn it off for a couple minutes and when I turn back on it works fine again but then repeats the problem. I've changed the door actuator and the fan motor. I've read about a faulty resistor for the fan motor but my year and model does not have it from all the pictures I've seen online. I've checked freon and it's full. Any help would be greatly appreciated.