air vents

1997 CADILLAC DEVILLE
129,000 MILES • AUTOMATIC
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DALE B
  • MEMBER
  • 1 POST
the vents in my 1997 cadillac switch dash to defrost and floor and back durring ac and heat operation
May 2, 2011 at 3:55 PM
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CARADIODOC
  • CAR REPAIR CONTRIBUTOR
  • 34,309 POSTS
If that occurs during acceleration, look for a leaking check valve in the vacuum hose feeding the heater controls. If it occurs when cruising at a steady speed, suspect a leak in that vacuum hose. Vacuum-operated systems are spring-loaded to default to the defrost position when there's a problem with the vacuum supply. Your feet might freeze but for safety, your windshield will be clear.
May 2, 2011 at 4:13 PM
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CADIEMAN
  • CAR REPAIR CONTRIBUTOR
  • 3,544 POSTS
in the l/f fender there is a canister in front of the wheel. you see a loose vacume hose thats needs to be reattached.look from the bottom.gl
May 2, 2011 at 6:45 PM
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.