Chevy Blazer 2002 LS 2-Door

When I turn on my AC (hot or cold) the air wont blow out my bottom vents. When I put it to feet, it blows out defrost. everything else works normal except that any lower vent setting comes out of defrost. I've already had the vacuum hoses changed and the guy i talked to said the next step is the black vent changer mechanism, or something like that. I think I found it way back behind my glovebox but i'm not sure if that's it. If it is, i have no idea how to get to it to change it. Also, I need to knwo how to take the back pannels off so i can get to my rear speakers to change them. Thanks for any responses.

 

Auto or manual HVAC?

 

Manual. Three **** AC unit. First for how hard the air blows(1,2,3,4), second for temperature(red and blue lines), and third for vent select or max AC.

 

Yeah, I know what there is on the manual controls. Diagnosis is different depending on whether you have auto or manual.

You could either have a problem with the HVAC control head (what has those three ***** on it) or with the upper mode door actuator.

Here is a schematic of the system:

 

I...have no idea how to read that. I believe that is what I am looking to get to though, the door actuator. How do I get to that? Or is that schematic supposed to tell me that? lol

 

The schematic only shows you how things operate, not where components are. The defrost actuator (aka upper mode door actuator) is located on the driver side of the HVAC housing and is accessible by removing the driver side and center lower hush panels. It will be on the side of the HVAC housing and have a blue vacuum line running to it. If it does not get vacuum when you change the modes to anything but the defrost, then there is a problem with the control head. If it does get vacuum, but does not move, then there is a problem with the actuator.