Mechanics

AIR VENTS STAY IN DEFROST POSITION

1997 Chevrolet Blazer • 130,000 miles

What is the problem? Vacuum or Blend motor?
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Pkimmel
May 24, 2012.



If your doors are operated by vacuum, they are normally spring-loaded to go to the defrost position when there's a leak or other failure of the vacuum supply. That's done for safety. Your feet might freeze but the windshield will be clear. Look for a small hard plastic vacuum hose under the hood. Be sure it's connected to the intake manifold and not cracked. There should be a small check valve too. You might have to temporarily bypass it to see if it's plugged or stuck.

Caradiodoc
May 24, 2012.