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Non AC truck. Should the dial slide all the way to cool?

Discussion in 'Tech Discussion' started by MisterB, Sep 19, 2019.

  1. MisterB

    MisterB Full Access Member

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    My temp slider stops right in the middle. I can slide it all the way to the right and it gets hotter and hotter as you get all the way to the right. The reverse happens and it gets cooler as you get towards the center and it stops and won't go any further. Should I be able to slide it all the way to the left? [​IMG]

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  2. eskimomann209

    eskimomann209 Full Access Member

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    Yes
    Check cable for damage or binding
     
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  3. 75gmck25

    75gmck25 Full Access Member

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    The cable runs across behind the dash to a temperature/blend door lever that is on the plenum behind the glove box. If you remove the glove box door you can see the top of the plenum, and watch the lever move back and forth. There is also a adjuster with a set screw to adjust the door for full travel.

    On the face of the HVAC plenum behind the glove box there is a plastic cover plate held on with a few screws. If you remove it you can see the blend door inside and watch it move. Its very common that something has fallen down the defroster vent and is inside the plenum blocking the door movement. Pens, pencils and small bolts are are a favorite.

    Bruce
     
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  4. MisterB

    MisterB Full Access Member

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    I lubed the cables you see at the top of the Pic. It's still not allowing full travel. Where is the plastic cover plate you're talking about? Can you point to it in my picture? [​IMG]

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  5. dvdswan

    dvdswan Full Access Member

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    Your cable is probably misadjusted. I don't remember which one is the diverter for heater/defrost or temperature. Look at the diverters then slide the temp in the direction you can move it and see which door has moved. Take out the screw that holds that cable and see if the door has more movement in the direction you had originally moved it. If it does then adjust as required.

    Be sure to measure the door direction in both ways.
     
  6. MisterB

    MisterB Full Access Member

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    I was starting to wonder the same thing. Does that mean when the control is in the middle, in reality it's as if it is all the way to the left?

    How do I adjust the cable?

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  7. dvdswan

    dvdswan Full Access Member

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    I don't exactly know the book procedure. As I said, find which one of the cables adjust the temp door. Then figure out which direction is hot and which is cold. Cold should close the door from the heater core. The cable will be all the way extended or all the in. Place the loop hook on the door actuator and bolt the cable down. Verify the function. Done.

    Note: I would verify that the lever mechanism in the dash is working properly first. I may be loose there.

    Here is a link to the service manuals.... https://www.gmsquarebody.com/threads/1973-1991-service-manuals.14499/

    It should have a section to tell you how to adjust the cables.
     
    Last edited: Sep 20, 2019
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  8. chengny

    chengny Full Access Member

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    From the 1980 Service Manual:

    Pages from ST_330_80_1980_Chevrolet_Light_Truck_Service_Manual.JPG
     
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  9. MisterB

    MisterB Full Access Member

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    I loosened the bolt, moved the lever all the way to the left and held it there while tightening it down. The lever moves past half way now, but only 3/4 of the way

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  10. AuroraGirl

    AuroraGirl Full Access Member

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    Sounds like maybe a rusted cable or binding maybe?
     
  11. Chevyguy

    Chevyguy Full Access Member

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    Or a critter nest inside by that diverter door.

    Clayton

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  12. MisterB

    MisterB Full Access Member

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    I'm just gonna pull the box and take a look.

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  13. MisterB

    MisterB Full Access Member

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    OK, I decided it take the box out. It's a little involved because the heater core hoses need to be removed and there are bolts inside the truck and inside the engine that need to be undone. Of course the cables need to be removed too.

    Guess what I found inside the box that was keeping the door from moving all the way? Let's just say I have another wrench today that I didn't have yesterday

    While I was in there, I put in a new heater core and all new hoses and hose clamps.

    Problem solved [​IMG]

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  14. Chevyguy

    Chevyguy Full Access Member

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    Good job, I just replaced my heater core. Did you replace the foam weatherstripping wherever you had a duct connection?. I used 1/4 inch window weatherstripping tape from Home Depot and it worked great. No leaks.

    Clayton

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  15. MisterB

    MisterB Full Access Member

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    Na, I just reused that rubber strip it had.

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