No air on driver vent only

Not to bring up a thread that is too old but my 95 and 99 have similar issues and I'm hoping I can fix it. I have good total pressure and cold temps.

When I am cycling through my modes it works correctly on floor, floor and upper, and defrost however when its just directed through the upper vents (not defrost) it bleeds out the floor and the defrost which causes the pressure to be less than ideal in these AZ summers. I have a new mode actuator, the linkage is correct and I can physically see the door rotating into the different positions in order redirect air to appropriate selected mode. If I manually put pressure on the linkage i can see the gaps close around the door and i get the pressure i need because it seals off the floor and defrost vents. Are these gaps that allow air to bleed into the floor and defrost vents caused by the foam getting pressed down and becoming flat over time? Does anyone else have this issue?

Thanks!

Is there another mode actuator lying around that you can try? It sounds like the actuator isn't holding the plate firmly enough and is letting air push by when the fan is on high. It's possible for the rubber on the edges of the plate to be worn, but if it works well when you hold it with your hand, it sounds like it's the actuator not holding it firmly.

For a quick temporary fix, you could duct tape the plate when it's in the upper position.

I'll go ahead and grab another actuator and see what happens. I'll let check back in when I get it figured out.

east302 said:

The duct sits/connects to the air distribution case indicated by the arrow. Once air passes through this, as directed by the damper controlled by the mode actuator, there is nothing else in the duct between that point and the dash outlets.

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east302 how'd you go about taking apart everything in the photo above? Air was working great up until it started getting hot. Now there's no air going to defrost or dash. Mode door actuator is fine, and I can get air out at the foot vent. I took off the mode actuator and pushed the plate manually and still wasn't getting any air at any position in defrost or dash, so I suspect that foam in your photo fell is off or clogging something.

Between this and the driver side window not working, I think my truck is trying to cook me.

That picture was from when I replaced the dash. Here's the write-up...

http://www.fullsizechevy.com/forum/...h/521791-1995-1998-dashboard-replacement.html

You may have to register to see the photos. Hope it helps. Pulling the dash is more time consuming than difficult. I don't know if you can access the a/c box internals another way, maybe someone else will chime in.

east302 said:

That picture was from when I replaced the dash. Here's the write-up...

http://www.fullsizechevy.com/forum/...h/521791-1995-1998-dashboard-replacement.html

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Amazing write up, thank you! I only have a minor crack on my dash, or else I'd use this as an excuse to replace it as well. I think I'll borrow a plumbing inspection camera and try to snake it through the ducts. From your photos, I really don't see how that insulation foam could separate and block the vents.

A camera is a good idea, maybe it'll show what is going on with it. Keep us posted.

jollyjerry said:

Amazing write up, thank you! I only have a minor crack on my dash, or else I'd use this as an excuse to replace it as well. I think I'll borrow a plumbing inspection camera and try to snake it through the ducts. From your photos, I really don't see how that insulation foam could separate and block the vents.

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The camera is the best idea I've heard in a long time. Thanks for sharing.

With the camera, I saw the part number 52469351, which is 34 in the picture above. I tried pushing the door with the camera, but didn't have any luck. Looking at the diagram more closely, I wiggled 35 and 36, the connection points for the top of the levers attached to the mode actuator. I had to push on it pretty hard before there was a whack and the door released itself. The rubber around the doors is pretty degraded, causing the doors to stick.

http://www.wholesalegmpartsonline.com/showAssembly.aspx?ukey_assembly=431109

What is the actuator doing when it tries to adjust the sticking damper? Is the position indicator dial on the actuator rotating smoothly or is it hanging up?