HVAC air flow is on half through the floorboard and half through the defrost ducts

1992 PONTIAC GRAND PRIX
80,000 MILES
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COVERLAND
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I have the car listed above 3.1 with a heater/AC problem. Fans work great, the hot/cold lever seems to change the blowing air from cool to warm, and the air output is split between the defrost and floorboard. It doesn't matter which switch I depress (AC, defrost, vent, floor, etc), the air flow doesn't change. Seemingly half through the floorboard and half through the defrost ducts. Even the fans speeds work fine. A couple of knowledgeable guys have told me they think the problem is in the 'blend back door actuator' but I haven't been able to find any instructions anywhere on how best to change this component and I had to wonder too, if there isn't some way to just run the AC compressor directly to the battery through a fused switch versus tearing into my dash when I'm not entirely sure what I'm looking for. Anyone have any experience changing one of these components?
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May 4, 2013 at 12:26 AM
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CADIEMAN
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the AC programer controls that door. Remove the glove box liner you will see the linkage hooked to a arm that is the programer.
May 4, 2013 at 1:06 AM
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COVERLAND
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So that's to say you think the problem may be with the AC programer?
May 4, 2013 at 9:21 AM
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CADIEMAN
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after reading through your question again. Your problem is a vacuum leak somewhere usually under the hood. You will need to check for any cracked vacuum hoses or leaks. I used to use a can of brake cleaner to spray on the vacuum hoses down. When you spray on the leaking hose or component the engine idle will pick up RPM's. Then you will and just need to repair the leak and the AC will come out the vents properly.
May 4, 2013 at 11:13 PM
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COVERLAND
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Thanks, I'll check for a vacuum leak today. I haven't checked to see if pressing the AC switch actually turns on the AC compressor when the engine is running and am guessing that if it were a vacuum leak, that wouldn't stop the compressor from running when the AC button is pressed. Thoughts on that?
May 5, 2013 at 4:59 AM
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CADIEMAN
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it should still turn the compressor on.
May 5, 2013 at 9:25 PM
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COVERLAND
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Is there some low Freon protective switch that prevents the compressor from coming on if the Freon is low? If there's a low Freon type switch that keeps the compressor from turning on though, how in the heck to they get it to charge back up...

I was wondering if there might not be two issues going on. One, the vacuum leak (or blend back actuator), whatever it is; and then the low Freon issue that may be keeping the compressor from turning on.

Kind of a frustrating deal but I'm not inclined to give up because the AC used to work great in this car..
May 6, 2013 at 6:03 AM
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CADIEMAN
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when you push the pin in on the valve does any Freon come out?you may have a leak somewhere. You can buy Freon with a gauge at the parts store. It's not that expensive. You hook into the low side valve. the two valves are different sizes so don't worry about hooking it to the wrong one.It has a red and green scale to make it easy on you.the gauge should only reading 30 pounds anything under that it is low anything over that it is over full.
May 6, 2013 at 4:19 PM
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COVERLAND
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And you can charge it without the compressor running ? (I haven't done an AC charge before)
May 6, 2013 at 5:58 PM
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CADIEMAN
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yes, but it needs to be under 30 pounds on the gauge.
May 6, 2013 at 6:04 PM