The Heater control

Discussion in 'OEM and Custom Interiors' started by John Carlsen, Sep 30, 2019.

  1. John Carlsen

    John Carlsen Newbie

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    I have just purchased a minty 1990 scsb K1500 with 54000 miles,.

    It has the dreaded digital heater control with servos to activate the doors.
    Most of it works. Vent , temp both go up and down as normal. the indicator shows what the system is doing. Are these even available to buy any more?

    The switch doesn't do anything when i push the defrost button. It stays on floor.
    The indicator also doesn't change just shows floor.

    Has anyone swapped one of the manual heater controls in ? Cables and levers.
    Will the cable control fit in where the digital one is?

    That would be so much more simpler to deal with.
     
  2. someotherguy

    someotherguy I'm Awesome

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    Nothing dreaded about that control - they usually don't go bad. It's the 95-up design that is fairly weak.

    Not sure exactly what's going on with yours at the moment but I can say there's no reason to fear it, nor to rip it out and sub the cable style setup which by the way is from a truck that is heat-only, non-A/C equipped.

    Richard
     
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  3. Jglew82

    Jglew82 I fix stuff

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    Agreed 100%, these control systems were pretty good. The original controls in my '90 are still going strong.

    Sounds like you just need to do a little troubleshooting to find your problem, op.
     
  4. DerekTheGreat

    DerekTheGreat I'm Awesome

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    These systems have been really reliable in my experience. Much better at doing what you want them to do than the Ford vacuum dashpot crap in their trucks. Sounds like perhaps your servo motor for the blend doors is bad. Mine was on my '89. I got a newer one from a junkyard, swapped it in and everything has been peachy since. It lives above the gas pedal closer to the trans tunnel. When you pull it off, be mindful of the linkage and lubricate the blend door shafts as you move them by hand. I used ATF when I did it.

    To verify if the servo motor is bad or the blend door is just sticking, have someone push FLOOR while you look at the linkage. When the linkage stops moving, have that person hit Defrost. If the motor moves but the movement is absorbed by those spring thingies, try helping the linkage by hand. With such low mileage I wouldn't be surprised if the shafts are all gummed up. If you get no movement out of the servo motor it could indeed be toast.
     
  5. M1Gunr

    M1Gunr Newbie

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    I have a 1 min video showing the servos and explains everything. I can't upload due to size.
     
  6. Schurkey

    Schurkey I'm Awesome

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    The only problem with the heater control I have on my '88 is that I needed to re-flow the solder a couple of times. The display goes dark. If I push on the face of the unit in a certain place with my thumb, it'll light up again (for awhile.)

    Wild guess: Your display is working just fine. You need to replace one or more of the actuators; or track down a wiring problem to the actuator.
     
  7. John Carlsen

    John Carlsen Newbie

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    Thanks for the info about reliability.
    I will investigate a bit more. It did work intermittently for a couple of days. Could be just the plugins have a bad contact.

    I did find a couple of videos on utube.

    I have had bad luck with the vacuum systems on the squarebodies.
     
  8. ZWilson07

    ZWilson07 Newbie

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    Ah the old vacuum days. How i dont miss them.

    Let us know what you find.
     

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