Dodge 2009 Durango - Manual (Page 282)

To change the temperature in the rear of the vehicle,
rotate the temperature control knob to the right or left.
The blue area indicates cooler temperatures while the red
area indicates warmer temperatures.
NOTE: For best operation, make sure that ventilation
grilles located in the rear storage area are not obstructed
by stowed articles.
Rear Storage Ventilation Grilles
280 UNDERSTANDING YOUR INSTRUMENT PANEL