2004 Dodge Durango Owner's Manual - Page 182

182 INSTRUMENT PANEL AND CONTROLS NOTE: There is a difference in temperature between the upper and lower outlets for added comfort. The warmer air goes to the floor outlets. This feature gives improved comfort during sunny but cool conditions. Heat (Floor) Outside air flows primarily through the floor outlets located under the instrument panel. A small amount of air is directed through the defrost and side window demister outlets. Mix Outside air flows in equal proportions through the floor and defroster outlet. Defrost Outside air is primarily directed to the windshield through the defroster outlet located at the base of the windshield and side window demist outlets. NOTE: The air conditioning compressor operates in both Mix and Defrost or a blend of these modes, even if the A/C button has not been pressed. This dehumidifies the air to help dry the windshield.