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Join Date: May 2001
Location: Roswell, GA
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Angry A/C Vacuum problems

I have a vacuum problem in my 87 951. (I think). Whenever I have the A/c on recirculate and apply the slighest amount of throttle to the engine...I loose the recirculate. The vacuum operated recirculate door opens and closes with the opening and closing of the engine throttle. I have tested the check valve and it is OK. Any other suggestions?
Thanks

Old 05-22-2001, 06:49 AM
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Can you be more specific? Do you mean the fresh air/inside air flapper? Or the Hot/Cold flapper? And how are the rest of your vacuum accessories working? Does your heater valve open and close when you adjust the temp?
Old 05-22-2001, 12:53 PM
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It is the inside/outside door. Everything else seems to work OK.
Old 05-22-2001, 01:49 PM
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I had a similar problem on my 84 na: when you accelerated with the a/c on, the center vents would stop blowing and warm air would come through. Turns out that the vacuum resevoir next to the battery was disconnected, so when you accelerated and manifold pressure increased, the blender door would close up. I reconnected the resevoir bottle and it worked fine ever since.

My recirculate on my 951 doesn't work at all. The a/c works fine, but is always pulling outside air. Is the recirc. vacuum controlled or electric? Where's the solenoid and door to shut off outside air? If it's vacuum, I'd say we both have a leak. Yours is probably small, mine must be major.
Old 05-22-2001, 02:24 PM
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Probably has nothing to do with the actual vacuum pressure in the system then, just coincidence that it opens under high vaccum. You should check the electrical connection between the switch and the vacuum control unit. I think the control unit for that is just inside the area where the glove box comes out, and attached to the wall on the left. I'll check the factory service guide for you when I get home. Anyway there is an electrical connection from the dash switch that controls when that vac solenoid opens. You should check for voltage to that solenoid. There are two there I just can't remember wich one does what. When the switch is not working or the solenoid leaks it does weird things with the mixing flaps. and the fresh air door.
Old 05-22-2001, 02:24 PM
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Is the AC check valve the black and blue one which taps into the brake booster line ?

Old 05-26-2001, 08:11 PM
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The vacuum acuator may have a leak or the line leadind to it.
Old 05-26-2001, 08:36 PM
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I did some more trouble shooting and found that the vacuum line going to a black bottle on the passengar side was off. I think this is some type of resevoir. I also took at the freshair flaps just outside the windshield against the firewall. I could see the squirrel cage fans and the flappers did not appear to be moving fully in either direstion. After I reconnected the line to the bottle the flappers moved all the way up thus causeing the a/c to be on constant recirculate. The switch on the dash has no affect. I also still have the original problem...but now I know it is not the flappers that are fresh air flappers that are causing the change in air flow during acceleration. I think the idea of the electrical issue might be the problem. Can we elaborate more on the electrical?
Thanks

Old 05-30-2001, 07:05 PM
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