Now that I've got an accurate reading on the outside temperatures, I need help with another HVAC problem. My heat and A/C both blow hot and cold respectively, but i'm noticing that it's only coming out of the defroster vent(s) on the very top of the dash against the windshield. I'm told that there could be a vacuum line messed up that it not activating the servo or whatever controls the doors that change the airflow direction. Where would I look for this? Any help would be hugely appreciated because it sucks when the A/C is on but you can barely feel it because it's coming out of the farthest possible vents.