Hey guys. 78 Malibu. Originally AC car. I have a Non AC box and an AC head unit. My blower works on all speeds. All vaccuum doors seem to work. I can visually see the middle dash vent one working and also the door behind the glove box. The cable driven “hot/cold” lever door by the heater core works as well. I am getting no air flow from any of the vents on any setting. Thoughts?