Air door actuator

[Airwinger]

I have a 2002 GMC Yukon Denali AWD. My a/c/heater vent is stuck on the top front defrost vent. When I cycle through the various different modes (front vents, floor vents, combinations) it will not work and remains on the top front defrost vent mode. I bought the new air door actuator and I'm ready to change it out but my problem is finding and changing the right one. Passenger side, driver side, back side, top side? Any help would be greatly appreciated. Thanks in advance.

 

[Texan]

Here is a thread about your problem

http://gmtnation.com/f23/2002-envoy-mode-door-actuator-replacement-2787/