The part is #7. There are two of them. This may be somewhat involved..........
Remove the glove box by backing out 3 @ 6mm screws
Remove 4 screws and take off the glove box door (optional - I didn't want to bend the piano hinge)
Remove the trunk pop connector
Remove the glove box light (optional)
There are two air mix actuators (electrical motors). The one on your left near the console (see pictures) controls the hot/cold signal from the passenger side setting.
Remove the plug to the electrical motor and remove 2 @ 5.5mm screws. The motor will slide off a white shaft. You can move this by hand if you temporarily want hot or cold air until you get your new motor.
Installation is the reverse.
Time to complete - less than 1 hour
Time to find the 5mm socket that you dropped between your seat and the console - 30 min
My heat now changes when I roll that little passenger ****!
Root Cause: I put a blower motor in about a month ago. There is a triangular mess of wires that I had to move out of the way to drop the blower motor. Apparently when pulling on those wires, I unplugged the air mix actuator. My clue? I saw the plug and thought "how the hell does it work without being plugged in?" (brilliant deduction I know).
Now in my defense, when you change the blower motor, you can't see that actuator because you don't remove the glove box. I didn't know it was unplugged and didn't need warmer air until it started to get cool.
I did quote a price on the electrical motor - about $100 from Rockauto.
The 2nd actuator buried deeper into the dash, but still easy to remove controls the driver'* side. For once, GM didn't hose us on a repair. This was easy!
I am going to go buy a lottery ticket.................