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

Tiny
HUBERTBOGDAN
  • MEMBER
  • 1999 CHEVROLET LUMINA
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 269,000 MILES
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?
Friday, April 24th, 2009 AT 12:57 PM

3 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,749 POSTS
Hi:
Does this seem to happen under acceleration?
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Saturday, April 25th, 2009 AT 10:34 PM
Tiny
HUBERTBOGDAN
  • MEMBER
  • 2 POSTS
Hi,
Yes, under acceleration, when I'm driving
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Sunday, April 26th, 2009 AT 12:05 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,749 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
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Sunday, April 26th, 2009 AT 12:35 PM

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