I'm pretty sure the blend door just regulates "how much" heat is added to the air based on your temp setting. Also pretty sure most cars have one. I replaced the actuator on my 97 F150 before I traded it, was right in front and took a couple minutes. Dumb move by Ford burying it. Turns a simple repair into a heater core type repair.

 

The blend door actuator went out in my XLT a few months ago. Under 30k miles. Truck was at the dealer all day, but they did the repair in under 8hrs.

 

shouldn't take a mechanic thats done 1 or 2 heater cores more than an hour to get the dash out, something like eight bolts holds it in, then you slide the whole thing onto the seats

 

I can tell you that when mine went, it was like 15F outside and I could not get the truck warm on the inside at all. I believe it actually regulates/blends outside air with existing air in the cabin. It would appear on mine that it broke in the full open position. This was on a Lariat with dual climate control, not sure which models have the same set up.