Heater not working...HELP!!!!

So...we had a brake controller installed and the hitch wiring upgraded to the round one....so after this was done the A/C did not work... The A/C works now, we did not do anything it just started working but the heater does not. It blows at all speeds but their is no heat. It stopped working, then it worked for a day and now has stopped again for the last week. I checked the fuse under the hood. It is good.. I have no idea if the installation of the brake controller has any thing to do with this?? It seems odd that after the wiring for the hitch and controller was done that the climant controll started to act up. we really do not know where to check next for this proplem..and would really like to avoid taking it to a shop.. so any help would be great. Is their more then one fuse for the heating system? is there a relay?

PLEASE HELP...
THANKS

 

sounds like the blend door motor

 

where do you access the blend door motor?