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This truck has been like this since I bought it but this is the first time I have had to drive it when its really hot out...I was burning alive in it today, 100 degrees eeeek! Anyway...the AC has just been converted to r134 a few weeks ago and is charged up and blows ICE cold. Problem is, it seems to blow about 90% to the floor and 10% out of the top vents, you can feel air coming out just when you are driving and its really hot outside, it freezes your feet but the rest of your body your still sweating. I tried taping off the vents at the bottom to see if it would direct some air up top and it made no difference. Please somebody tell me any ideas on how to fix this!?! Going nuts! EDIT: Forgot to mention that most of the people I saw on here with the same problem say that it blows from the defrost and the floor and not the dashboard vents. That is not the case for me, the defrost doesnt blow anything and the dash blows a little and the floor a LOT. The fan kicks on LOUD and sounds as if its blowing a lot of air (well it is, out of the bottom) so I dont think the fan is the issue. Also, when changing the selector switch you can hear the vacuum and it sounds normal.
 

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I have the same problem with my 91 dime...I know this is the wrong section for my problem but from what I undersatnd I think I have heard alot of people saying it is a vacuum problem. Anyone konw if this is true?
 

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same problem.. 91 dime...:D
 

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Well I have checked everything under the hood for some sort of a vacuum issue, pulled the underdash cover off to look under there and I cant really see any vacuum lines that could even be leaking. Would I need to look behind the dash behind the HVAC controls?
 

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If you pull out your heat AC controls you will see at the bottom of the assy. a little round thing with a bunch of diffrent color tubes going to it. This is the vacume control valve that changes the vent settings from floor to dash, defrost you can jumper it to make it do what you want or replace it I got one from the JY for cheap. make sure you test it before you put it all back together.:rant:
 

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There are a few diaphrams underneath you dash which this controller feeds the vacuum from the engine too.

Start on the engine side and make sure you are getting vaccum through the firewall. Should be a main line going through a grommet near the back of the engine.

There should be 2 diaphrams on the driver's side, just above the accelerator pedal. The lower one's for the upper vent vs. floor, the upper is the defrost to the windshield. When you select the upper vent, tha diaphram should get vacuum, and the little arm should pull the redirection flap. You should be able to see/hear it do it with a flashlight on it. I suspect the supply line is off, or you aren't getting vacuum from the engine (plugged/broken line). Could also be the control unit as mentioned above...

Good luck
 

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did you check those diaphrams?

I have my plenum out from my donor truck. Looks like standard position is to the floor.

If ALL of them aren't working, it's the supply vaccuum or the controller (actual little rotating gear wich switches the vacuum. Note: There's also another diaphram on the passenger side (in the wiper cavity - whatever that's called). That's for the outside air vent flap.
 

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I had the same problem and it was both a vac leak and my clip was broken. here is a break down and part #.
Do you have a bigger picture of that? I've been having this problem too, and I think I've narrowed it down to this being the problem. It's just haard to get to.
 

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I have had the same problem. Read here and there that it was the vac selector. I had the truck in the shop for some other things that one of them, and the guy said due to a solenoid leak on the transmition, it was sucking trans fluid into the vacuum lines and that ate through the line and created a pin hole. The pin hole makes a whistle noise behind the A/C selector. 4 hours later and I have a jimmied A/C selector that blows correct vents only on MAX A/C. However when I have my foot on the gas i dont get hardly any air until i decelerate.

And I empathize man, Im in Florida 100% humidity and 95-100, on leather seats.
 

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My 88 was like that and it was the clip broke off that open and closes the door. I just zip tied it open for now since I am more worried about my ac here in az. I'll get the clip this winter I guess.
 
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