air vents keeps switching on and off


Old 06-26-02, 07:37 PM
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air vents keeps switching on and off

i have a 1992 astro van 3.4 engine, when i run my air im getting the vents not working all of the time. it comes out but then it switches to the defrost or on your feet . i dont notice a change in the fan just where the air comes out. it might not do it for awhile then it starts acting up.
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Old 06-27-02, 01:03 AM
Join Date: Dec 2001
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it is likely a vacum leak or bad vacum check valve that comes from the engine and goes to the control head.
Old 06-27-02, 02:31 PM
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where might i find this check valve?. can i buy this at a auto store or is it a dealership part?
Old 06-27-02, 02:33 PM
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Look under the hood and see if there's a vacuum diagram under the hood. If so, it might show it there and the approximate location.

What that being said, most times an AC Delco distributor would have it...same as the GM part.

On some GM's, there is a vacuum wheel at the back of the A/C controller. That goes bad and you'll hear hissing from behind the dash....sure fire sign of that valve going bad. On an old car like the GM's I have, it's an 8 dollar part.
Old 06-28-02, 04:16 PM
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Its funny your having that problem, because I just fixed my mustang, it was doing the same thing, all I had to do was replace a couple of vaccum canisters underneath the dash, they had leaks, I replaced a couple of those and it works fine now.....

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