Using either the AC or the Blower the vents switch from panel to defrost.
Sep 1, 2010 at 7:51 PM
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JACOBANDNICKOLAS
✓Experienced Mechanic
110,246 POSTS
You are looking for a vacuum leak in this case. Check under the dash first. If you are really lucky, you may hear a hissing sound with the engine running.
Let me know what you find or if you have other questions.
Joe