My Durango is my second vehicle. So when I do drive it, I need my babies to bee warm. I noticed the rear heat is not working. Its blowing cool air when you use either front or rear control. My husband dismantled the plastic panels in the back and saw that the knob would make the flaps flip. And obvious we are getting air. Im not sure how much air should be pushing through. Anyways, I would really appriciate some ideas to try. Specific part names and locations would be helpful for a do-it-yourselfer.

Thanks for you time, cheers.
Durango mamma