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Fresh Air Vent Question

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by RiceDaddy, May 25, 2003.

  1. RiceDaddy

    RiceDaddy Registered Member

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    Well, it finally rained here, which is very rare. This gave me the opportunity to remember that I had a water leak that was wetting the passenger-side floorboard. I searched the forums for background info and then set into finding the leak. On the passenger side, I pulled off the plastic panel that holds the fresh air vent valve and the vacuum actuator that controls it. Also pulled off the plastic cowl grill so I could look down there. After getting everything apart, it looks like water is getting into the cab through the seal around the fresh air vent, so I plan on replacing that seal. Water flows down from the cowl area and past the fresh air vent normally, but with the bad seal, it looks like it's creeping in there. The valve itself isn't leaking, just the seal around it. I thought I would bring this up here because from the posts that I read, this hasn't been mentioned yet.

    Since I had the air vent out, I started playing around with it and it looks like the actuator isn't working because I couldn't get the valve to move, except by hand. Under what conditions is this valve supposed to be open and shut? What purpose does it serve? I haven't checked to see if I'm getting vacuum at the actuator yet, but I thought I'd see what this thing was for. /forums/images/graemlins/ears.gif
     
  2. wrathORC

    wrathORC 1/2 ton status

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    I was wondering the same thing. Mine wasn't even hooked up from the factory (!). The vacuum line was hooked on the pin-type tang that locks it on but not actually on the vacuum motor. My Dad saw that and hooked it up right when we were installing my stereo last summer and we attributed it not being hooked up to the same goofball that mixed up the passenger and driver side speaker wires on assembly.

    I later tried the vacuum motor and it works because I tried it on manifold vacuum.

    I played with it and it never worked. I thought maybe it was for MAX AC which on newer vehicles uses recirculation but it didn't work then either. Maybe this was soemthing GM never actually finished when they designed it? Hopefully someone else knows.

    I don't know. I pulled my vent out and replaced it with a non-AC (manual) one. The old one is sitting in a box looking for a purpose in life.
     
  3. Confedneck

    Confedneck 3/4 ton status

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    you set the a/c on "vent" to get that vent to open on the passenger side... im pretty sure you can swap out for a drivers side manual style one...
     
  4. Itali83

    Itali83 1/2 ton status

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    Actually, the fresh air vent door is open in all positons except MAX a/c. This is done to make sure you have a positive flow of fresh air in the cab. It's probably a bad diaphram or broken vacuum line thats the problem.
    Ben 87 Jimmy + 89 Blazer
    /forums/images/graemlins/usaflag.gif
     
  5. RiceDaddy

    RiceDaddy Registered Member

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    I did some testing with it today. I unhooked the vacuum line from the actuator. The only time I get vacuum in the line is when the A/C is set to Max. The door is spring loaded to be shut under no-vacuum conditions. After hooking the line back up to the actuator, as soon as you turn the A/C to Max, the door opens. So it appears that the actuator is working, but this seems opposite to what you just described. /forums/images/graemlins/1zhelp.gif
     
  6. RiceDaddy

    RiceDaddy Registered Member

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    After scratching my head on this one a little longer, I realized that I was overlooking that the blower fan suction was just on the other side of the vent valve in the fender. Under normal A/C operation, the vent valve is closed and the blower sucks air in through the cowl and from down below the truck. When you set the A/C to the MAX position (re-circulate), the vent valve opens. Now the blower suctions mainly off of the air in the cab through the open valve. Voila, re-circulation.

    Sometimes the obvious eludes me. /forums/images/graemlins/tongue.gif

    rice
     

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