Hey man I'm also in louisiana had the same problem it was the air chamber box. What probably happened is the door for defrost and possibly others are broken. Causing air to pass through. Go ahead and check your mode actuator it's located to the right of gas pedal and pretty high up. Check to...
http://www.thetruckstop.us/forum/threads/rotate-dash-replace-defrost-door-hvac-flow-distribution-flap-box.31159/
This is the write up I used pics are not coming up. Not sure if it's much help now. And I used about a 3 minute youtube video for rotating the dash can't seem to find it. Will keep...
You have to remove seats, drop steering wheel column. And rotate dash foward, you don't have to remove dash just tilt it to foward position. Then you can see the culprit right in the middle. They sell the whole top part of box with 2 new flaps installed. Just unclip 3 fasteners 2 easy and one...
Had to do mine last summer as it was broken and hanging inside the box. This Is a pic of the blend box behind the dash from the top. Each door is connected to those actuators.