when I turn on heat or air in the rear It makes a clicking/popping noise help on 2003 Ford Expedition

when air or heat is turned on in the rear of car there is a constant clicking noise it is coming from the passanger side of suv back in third row vent area, what is this . make it stop

Asked by for the 2003 Ford Expedition
agree with #1 should cost approx 200.00 to repair
are we talking 200 at repair shop or do it my self,
I had the same trouble. I found both on Amazon for under 100.00 I put them myself. it took some time to pull the cover off but i did not have to remove it. Just moved it far enough away to remove the two actuators. The actuators are different so make sure to put the right one in the right spot or it could break.
2 more answers , 2 more comments
It's probably the actuator, gears or the door in the rear a/c/heater.
can I purchase the part and do it myself
You need to remove the panel to verify which one, and they are available at the part stores. Seek some help to install it.
It is the blend door in the rear right side. It is sticking or the actuator is stripped out.