02 GMC Sierra HVAC Control problem

Currently my control setting is stuck on defrost. All other controls work, i.e., the fan blows at all speeds, the temp control works, the AC works etc. No matter which way I turn the knob, (floor, face vent, etc.) it will not kick off of the defrost setting. Currently, since it is hot in Cali, I have the AC running, and it blows cold, but since it is stuck, the only place that gets direct air is the back seat and the windshield...ha! I searched the threads and found a '95 with a similar problem (the actuator that controls the flap) and my guess is this is the problem. Does anyone know where that is on this model, or if that is the likely culprit?

Also, I took out the dash control unit and made sure all prongs were straight and clean...that didn’t seem to help.