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Discussion Starter · #1 ·
Hi folks, on my '96 the HVAC air distribution knob doesn't entirely work, and today I figured out why while I was re-wiring the brake controller under the dash. I feel like I'm missing some pieces under here or something is not connected properly. The motor works fine and moves the lower linkage in the photo, but the upper one is just hanging free. If I move it up and down by hand it will change the air flow from top to bottom.

Can anyone post a photo of this same thing showing what it is SUPPOSED to look like?

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Yes your right.There are a few pieces missing.I had to buy replacement parts from both eBay and the GM dealer to fix that section.I’ll see if I can find a picture.I used to have one on my iPhone.
 
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Here’s another picture I found of the same thing.
 

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So that is what those little springs and plastic pieces are for.
 

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Discussion Starter · #6 ·
Thanks ya'll, that's helpful! I wonder how my truck came to be missing those parts :). What's funny is the PO had a little carabiner hanging off one of these, using it to support wires coming out of the back of the trailer brake controller. It will actually switch to defrost OK, but on any other setting the air just kind of blows out wherever it feels like. I think I have one of the plastic springy pieces (the upper rear one) but I'm missing the forward one.
 
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I would not think it would be too hard to find those parts if you got a junkyard near you . Any full size truck 95-99 would have them, maybe other years too. The springs are there so if something had fallen down the vents it doesn't just destroy things. If something is jamming the vent the spring should just compress.

The way they fit the vent doors inside the box is they are slightly undersized so the shove them in at an angle and get one shaft in then the other size will just clear to shove down into the duct. Once its in they center the blade and stick a hardish tar like gasket weather stripping like crap along the edges of the blade that takes up the gaps and makes a better seal. These keep the blades centered so the shaft nubs barely stick out the box to do their thing.

Over time and with crap falling down the vents like say a pencil this tar stuff can get knocked off and that will then let the blade float enough in the duct for the shaft to fall out its pivot hole in the duct. Depending on which blade falls off it may fall down into and jam the other blades. Your stuff all missing makes me think someone has been in there working on things and the only thing to really work on is when the blades fall apart like that.
 

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Discussion Starter · #8 ·
@57diesel Now you have me a little more concerned! Wasn't planning to tear into that whole system right now if I could just fix the linkages for a while. The defrost works at least, which is somewhat mission-critical, but the floor/dash vents do not fully adjust as it sits. You just get a little air coming out everywhere :)
I may have a to schedule some 'down time' to do a more detailed teardown and inspection later in the year.
 
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Go here, down to post #18, for some photos of the a/c box internals.
 
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