Question about 2003 GMC Sierra 1500

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Air goes straight to defrost

Air blows out of front vents at first then it goes straight to defrost no matter where it is set.

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  • arnold_y Apr 12, 2009

    simpsonite, everything seems to be electric. not vacuum.

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You have a vacuum leak! Defrost is the default position. You need to find vent vacuum lines on passenger side near firewall under hood or under dash.

Posted on Apr 12, 2009

  •  Ben S.
    Ben S. Apr 24, 2009

    You need to locate your a/c cannister (under hood). Its most likely a short cylindrical shape. There should be two small vacuum lines. Follow those lines to your firewall and to the other side (passenger side) Check for leaks. It is possible you might need to remove part or all of your dash board. Its a tiny problem that can sometimes be a ***** to fix.

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