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  1. #1

    Default Defroster blows all the time... In addition to other vents

    I noticed that my defroster is always blowing air out, even when the control is set to vents or floor. The air doesn't ONLY blow out of the defroster, it also goes to where the selector is pointing. Is this likely an actuator motor issue or is it likely something else like a broken door?


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  2. #2


    My Tahoe had a similar issue I resolved it by turning on the a/c which took it off defrost.

    Here's the link to my post.
    Last edited by Conlan Rose; 08-15-2012 at 02:26 PM.

    1996 Chevy Tahoe LT 5.7L V8 4X4 205,000+ miles. Built proudly at Janesville Assembly in Janesville, Wisconsin
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  3. #3


    Tom, it is probably the defrost actuator, that doesn't mean it is broken, it may only need to be reset.

    The easiest way is to pull the HVAC fuses and re-insert.

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

  4. #4


    Thanks guys... The problem is that when I run the AC in the evening or after a rain, the windshield fogs over on the outside. I have had the battery disconnected several times for other reasons and it is still doing it. It is almost as if the defrost door never fully closes. It does blow harder through the defrost vents when I turn the dial to the defroster, but that might be due to the other mode door closing and forcing all of the air into the defrost duct.

    It would be nice to have all of the air coming out of the dash vents on a hot day instead of having it split with the defroster.

  5. #5
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  6. #6
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    Maybe the mode actuator sticking linkage or something blocking it.

  7. #7


    Now that I think about it, I did run a 4 AWG cable from the fuse block under the hood and into the cab to an auxiliary fuse block under the ducting on the floor... I might have routed it in such a way as to get in the way of something. I will have to look into that... Thanks a bunch for the idea!

  8. #8


    I moved the wire, it was close but not actually obstructing anything. The motor does turn and the linkage moves smoothly. I can't be sure it has full range of motion. Maybe there is something in there keeping it from closing... Now I have to figure out how to take it apart to look inside... Anyone know how this thing mounts up? I REALLY don't want to remove the dashboard!!!

  9. #9


    Theres really no way to get to the air system with out removal of the dash I figured that out with I looked at it on my truck. Also there is a metal bar across the width of the truck tat is in the way.

  10. #10


    I have the same problem with my 97 Sierra I was wondering if you ever were able to find a solution to the problem.

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