I had this problem in a 98 LSS, and found it described on a web page I can't find any more as a common problem. Anyway, the problem wasn't in the Vacuum Air Control per se, but really in the connector in the side of it used to hook it up to the vacuum lines during installation. Apparently the vacuum lines tend to collapse inside the connector. I removed my Vacuum Air Control, cut the vacuum lines on either side of the connector and tossed it. I connected the vacuum lines with hose that fit around the OD of the vacuum lines. Just get hose that fits tight around them - you don't want to use grease or glue or anything. Total repair cost under $3.
Install notes: I don't remember much, but be sure to mark the hoses so that you know which lines to connect when the box is reinstalled. Also, make sure you reconnect the mechanical vent arm to the actuator on the bottom of the box in the same position it was when you disconnected it.
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I have a '97 LSS that had the same problem. There is a large black plastic box where all the air lines connect that go to the respective vents; dash, floor, defrost, and rear on console. It is called the Vacuum Air Control. They get stuck, don't ask me why. My air would only blow through the defrost and it was terrible since I live in Dallas. Buying one from a GM dealer will run you about $700 (!!). Call salvage yards and you can find one for $50-$80, BE SURE you get they'll give you money back or exchange if it doesn't work, because the first one I got didn't work. It'll cost about $100 to get it installed, be sure the mechanic has done it before because it has a lot of vacuum lines in it and you don't want them to get crossed or leak. Hope that helps.
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I have a 96, and asked the what salvage yard question. Anyway if this is the same part you can get it for $31.99.
This part seems to technically do what the OA stated his part does. This part looks to have vacuum line attachments that would go to different dampers in the air system.
Though OA may be describing a plenum where there are dampers for each vent? If I find that part I'll update my answer.
Here''s the Google - http://www.google.com/products?q=olds+lss+96+Vacuum+Air+Control&ie=UTF-8&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1
Also, if you need an AC Compressor I found a place that has them for $204.00 rebuilt, instead of used. They have a lot of parts at decent prices. I have no affiliation. I was almost going to by a used compressor for 100.00 and decided to look more and found them.
Main Page
http://www.directauto.com/index-exec/
Compressor Page
http://www.directauto.com/category-exec/category_id/43/nm/AC_Compressors
the heat blows out the defrost when it should blow out floor vents only
Check upstairs heating unit.
Most likely a bad or disconnected vacuum hose to the defrost/floor selector in the heater ducting.
There may be several reasons why the air only blows out the front vents and not on the floor or the defrost on the 2003 Dodge Ram. The fuses may be blown, or the heating coil is not working correctly.
The 1979 Chevrolet Corvette air flow door might the stock in the position so that air only blows out of the floor vents. The air flow door is located next to the blower fan.
I have the same problem. Did you find anything out to help?
is it possible that the vent hose are disconected?
A weakening of the supportive muscles and ligaments of the pelvic floor, this condition, which affects women causes the pelvic floor to sag and press into the wall of the vagina.
the darkness and the weather condition
blower motor resistor
Air vent. It blows under front seat and into back.
I'm sure many factors are involved i.e. condition, original parts being present. I just purchase one for 80 bucks and it's in good condition and missing original finial. I would like a more expert opinion though. Walt