2010 GMC Acadia Owner's Manual - Page 256

8-12 Climate Controls N (Air Delivery Mode Control): Press to manually change the direction of the airflow. Repeatedly press the button until the desired mode appears on the display. Air Vents Use the slider switch in the center of the outlet, to change the direction of the air flow. Use the thumbwheel near the outlet to control the amount of air flow or to shut off the airflow. Keep all outlets open whenever possible for best system performance. Operation Tips . H (Vent): Air is directed through the overhead outlets. ) (Bi-Level): 6 (Floor): Air is directed through the rear floor outlets, as well as the overhead outlets. Air is directed through the floor outlets. The rear system floor outlets are located under the third row seats. Clear away any ice, snow, or leaves from the air inlets at the base of the windshield that can block the flow of air into the vehicle. Use of non-GM approved hood deflectors can adversely affect the performance of the system. Keep the path under all seats clear of objects to help circulate the air inside the vehicle more effectively. If fogging reoccurs while in vent or bi-level modes with mild temperature throughout the vehicle, turn on the air conditioner to reduce windshield fogging. . . .