1993 suburban
V8 5.7 litre

I get air flow from the vent and floor settings but nothing from the defrost setting. It whistles and seems like the blend door actuator is not working but i cannot find the actuator for the defrost. I took out the glove compartment and found the actuator that controls the hot and cold settings but nothing more. Any help would be appreciated.

 

Welcome to the forum.

There's got to be a door and actuator that directs the air to the floor of defrost. Just don't know where it is. Maybe someone here knows the answer.

 

did you pull out the radio and look back there? this system is all electronic so there should be like 3 or 4 of these actuators back there. I saw a few when I replaced the stereo but I didnt check their function.
Also look under the dash to the right of the steering column and see if you see anything.

 

I cured this problem and posted the answer in a similar thread. Crawl under the dash and lubricate the top door lever and that should fix it.