Question about 1997 GMC Sierra

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Window defrost I only get heat out of the center vents no matter where my heat selector switch is. I need to get heat out of my defrost, how can I get heat out of more than just my center vents. Dan from Washington State

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  • Roy Crowell Oct 05, 2011

    a diagram

  • Roy Crowell Oct 05, 2011

    a diagram of the vacum for the defrost for a 94 pontic grand am

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Check your vacuum lines....i just had the same problem with my gmc Sonoma. Somehow a vacuum line came off after being to a mechanic...the mechanic couldn't figure out where the hose went so he plugged it with a screw and low and behold the heat switch started switching between window, dash and floor like it was suppose to.

Posted on Nov 01, 2012

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It all has to do with vacums basically, when you turn the switch to defrost there is a hose that should **** a "door" so to speak over lettin the air travel through your defrost vents, and if your not gettin suction the in aint gonna switch over, and are you gettin it out of the floor vents?

Posted on Feb 11, 2009

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