I have a 2002 Yukon Denali and recently the Mode Control has stopped diverting air to the defrost ducts. Before you answer, I have verified that the Mode Actuator is working and shifts the white gear whenever I move the dial to each position. Even when I move it to defrost or any combination with Defrost, the gear moves, but no air comes out of the defrost ducts. I'm at a loss.
from what you are describing sounds like the door is broken on the inside then, if this the case then depending on where the door is located you may have to cut the housing open to access it and replace the door then seal it back up. but I would make sure this is the case before proceeding with anything unnecessary, I would pull the actuator off and see if you have can move the door by hand usually what happens is the plastic part that the white gear goes into cracks (inside the housing).
I was afraid you were going to say that. It seems that although I can get some air on the floor and and through the dash vents, It never seems to fully direct the flow (and never through the defrost). I haven't been able to find any diagram to help figure out what maybe going on.
I don't think there really is any diagram, there is some parts diagrams but it only shows which way the vents go and where the sensors are etc. the doors inside the vents are square and have a foam seal around the outer lips and have a hinge part, one side just sits and moves freely the other side connects to the gear on the actuator. if you pull the actuator off you can use a small tool or sometimes your fingers and you can move the door by hand it should move freely if you look inside with a flashlight you should be able to see if the plastic is broken or not. search on google for youtube videos they can be helpfull to better explain how it works.
