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air is stuck on defrost

This is a discussion on air is stuck on defrost within the Technical / Maintenance forums, part of the General Discussion category; i got a 00 sierra, and 1 day my heat decided to stay on defrost. no matter what i turn ...

  1. #1
    Greater Made Chevrolet
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    air is stuck on defrost


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    i got a 00 sierra, and 1 day my heat decided to stay on defrost. no matter what i turn the knob on, the air still comes out of the defrost vents. i tried changing out the HVAC controls but that didnt do anything. please help. thanks.

  2. #2
    Greater Made Chevrolet
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    Re: air is stuck on defrost

    bump, i hope someone has an idea. after doing some searching i read it could be an actuator? but what does it look like and where would it be? thanks.

  3. #3
    Registered User 1988c1500's Avatar
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    Re: air is stuck on defrost

    To start with I'd go to a parts store website or Rock Auto and look up pictures of actuators. Keep looking and you should find pics of them all. Then look under your dash and see if you can find them. A lot of time the gears in one will strip or jam but you can see it trying to move or hear it clicking.

  4. #4
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    Re: air is stuck on defrost

    i found the actuator, is there just 1. i took it out opened it up, gears look fine, and hooked it up to the battery and watch the motor turn the gears, so i assume its fine??

  5. #5
    Registered User 1988c1500's Avatar
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    Re: air is stuck on defrost

    On my '93 there was one to switch between vents and defrost, one to vent the cab when you turned the truck off, and I think one other one.

  6. #6
    Registered User mpope2's Avatar
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    Re: air is stuck on defrost

    The blend door itself could be defective


    00 Sierra Z71 ECSB, Keys, Zone 1.5"" BL, 16x8 ProComp 6079s, 315/75/16 BFG A/Ts, MSD 8.5mm Wires , Vette Servo,40 Series, 6 on Hi, GT5 4:10s, 212k mi

    94 Chevrolet K2500 L/D ECSB, 5.7,4L60E/HD2, 9.5 14 Bolt, 205k mi

  7. #7
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    Re: air is stuck on defrost

    i cant find the blend door actuator, surely someone might know! lol

  8. #8
    Registered User east302's Avatar
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    Re: air is stuck on defrost

    You should have three actuators that control the air doors:

    1. Temperature (hot/cold, diverts air to or away from heater core)
    2. Mode (floor/dash/defrost)
    3. Air inlet valve (Recirculation or fresh air at the blower)

    Here's a diagram for a 2000 with manual controls (versus the electronic ones sometimes used in Tahoes and Suburbans). The view is from the engine looking through the firewall--right is driver side, left is passenger.



    Part 3 on the diagram is the Air inlet valve actuator
    Part 14 = Mode actuator --which I what I think you're looking for, should be to the right of the gas pedal
    Part 19 = Temperature

    There should be a small notched cam or position indicator on the actuator. Watching that indicator, select floor, vent or defrost on the control panel and see if that cam turns.

    Hope this helps.
    Last edited by east302; 02-05-2011 at 11:44 AM.
    1998 Chevrolet Z71, 350 auto
    2003 Chevrolet Tahoe 4x4, 5.3L

    When I die, I want to go peacefully in my sleep like my grandpa, not yelling and screaming like the passengers in his car.

 

 

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