Rear air issues, noise in cargo area
 

Hows it going, hope someone can help me. Whenever the rear air is turned on and the thermostat is adjusted all the way HOT or COLD it makes this loud noise in the back driver corner like a bomb ticking, but much louder and harder. I read somewhere about a blend door actuator motor or something. Can anyone help me out, what the problem is and how to fix it?