My AC will begin to blow warm air on trips of about 3 hours or longer. It starts out fine, perfectly cold air. After a few hours the driver side will feel warmer than passenger side. Eventually it will become warm, and the passenger side will also start to become warm to the point where there is no AC at all. The AC compressor is still on and cycling when this happens. Once the car sits for a few hours the AC works perfectly again. My thought is AC Evaporator freeze over. I checked the cabin air filter and cleaned it with no better results. I also just checked the evaporator drain and it is clear. Would low refrigerant cause this problem, or something else? I guess I need to check refrigerant pressure next. Any thoughts?
-Matt
2012 Edge SE