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

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?

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi:
Does this seem to happen under acceleration?

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Saturday, April 25th, 2009 AT 10:34 PM

HUBERTBOGDAN

MEMBER
2 POSTS

Hi,
Yes, under acceleration, when I'm driving

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Sunday, April 26th, 2009 AT 12:05 PM

JACOBANDNICKOLAS

MECHANIC
109,885 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