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  1. #1

    Default Front defroster does not work

    Good Afternoon,
    I have a 1989 Z-71 whose defroster does not work. I get plenty of heat and full force fan from the center vents but not the top defroster vents. I changed the switch on the front of the "box" that controls an internal flap. I have the dash semi dismantaled but I do not see any other switches that may be the culprit. Can someone offer what else to check or what the real culprit may be?
    Thank you for the help.
    '89 Z-71 4x4
    '83 300SD Mercedes
    '94 C280 Mercedes
    '87 300TD Wagon

    If it ain't broke tear it apart and find out why...:great:

  2. #2
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    stephan's Avatar
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    Default

    Hey Crashone, welcome to the GM Truck club. I don't know if I can give you a solid answer on this, but is the switch actually moving the flap now? If the switch is working & you can see that it is moving the lever, maybe the lever is not connected firmly to the flap. Can you look in there with a mirror & a flashlight & see why the flap is not moving?
    1988 Chevy C-3500 2wd (no pic)
    350 c.i. 5.7 L Stock Block, 4 Bolt Mains
    L-31 Vortec Heads, Edelbrock Cam & Intake,
    Holley 650, Flowtech Headers, Magnaflow exh.
    Jet Trans 700R4, B&M Ratchet, 4:10 gears,
    3" susp. lift kit "shadetree"
    No rev limiter, No speed limiter lol


  3. #3

    Default

    Thanks for the reply. I can move the flap by hand but can't tell if the switch is moving it or not. I found a site with an exploded view of the system and it shows 2 switches (actuators) for the different flaps. I'll have to check later and see if I can see another one.

  4. #4
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    stephan's Avatar
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    When you move that flap by hand, does the air change to the defroster vents? If so then you know that is the correct flap & not the other one. If it is the correct flap then the switch is not connected to the lever for some reason, or the lever may have broken off the flap.

  5. #5

    Default

    Could be a problem with the control head itself. The motor down by the gas pedel is the one that controls where the air flows (panel vent, defrost vent, heat vent), you can remove the motor and move the linkage by hand to see if the flap inside is or is not working. By moving the linkage by hand it should change the flow of air from defrostor to heat to panel vents. If replacing that motor does not correct the problem then it may be the control head itself.

  6. #6

    Default

    Some makes and models do have heated windshields, not many, but some do. They do not have the wires like the rear window, and if they are cracked or broken they cost alot to replace, the technology is just not there yet to make it cost effectiv.
    ___________
    Canopies | Portable Shelters | Pop Up Canopies

  7. #7
    Jr. Apprentice
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    Default

    go under the hood and check the vacuum lines at the cowl that come out of the vacuum amplifier. They rot and break common problem

  8. #8

    Default

    check and see if you can hear the flap closing when you switch it.

    I had the same problem with my my 89 a couple years ago,because it had sat for a while before I had bought it. It wouldn't switch to heater, just defrost...I finally ended beating the "box" with my hand while I operated the switch...whatever had caused it to stick freed it up and I haven't had an issue again....
    89 chevy stepside off road
    03 suburban Z71
    03 Yukon SLT

  9. #9

    Default

    Does it actually heat up? Or is it luke warm. My vents stick from time to time, but it does switch.

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