I own a 2006 Buick Rainier CXL with the 5.3L V8. Had an intermittent issue with no A/C air coming from the front vents, only side and floor. Used to fix it by turning off the HVAC, waiting a few seconds and turning on AUTO. Now it's failed completely - no air at all. I get cool air from the front side vents and the floor. If I hit the front defrost button i get cold air from the defroster vents. I'm guessing, based on internet research, that there is an issue with the blend controller. I tried the "re-calibrate" process (pull fuses, etc.) but no dice. My problem is, where is/are the blend actuator(s) and how do I access them? How can I test it/them? What P/N(s) do I need to get? Need to get this fixed before the weather heats up! Thank you!