1999 Chevy Lumina Air flow inside of the cabin: upper &

1999 CHEVROLET LUMINA
269,000 MILES • 6 CYL • FWD • AUTOMATIC
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HUBERTBOGDAN
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Air flow inside of the cabin: when the air selector is on direct flow –The air is coming from the right air vents, after 3- 4 minutes, the air flow is diverted to the lower vents (nothing is coming from the upper vents). The air flow is switching from upper to lower vents all the time. Do you have any suggestions? It is easy to fix , any recommendations?
Apr 24, 2009 at 12:57 PM
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JACOBANDNICKOLAS
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Hi:
Does this seem to happen under acceleration?
Apr 25, 2009 at 10:34 PM
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HUBERTBOGDAN
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Hi,
Yes, under acceleration, when I'm driving
Apr 26, 2009 at 12:05 PM
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JACOBANDNICKOLAS
  • CAR REPAIR CONTRIBUTOR
  • 110,190 POSTS
The vent doors are run by vacuum. When you accelerate, the vacuum pressure in the engine lowers. You must have a vacuum leak in the system. Check under the dash near the controler, under the hood, anywhere there are vacuum lines tied into the vent system. With the engine running, you may be able to hear a hissing sound where the leak is.

Let me know what you find.

Joe
Apr 26, 2009 at 12:35 PM