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Heater Switch Wiring

Discussion in 'Early CJ5 and CJ6 Tech' started by Charlie Wells, Oct 15, 2019.

  1. Oct 15, 2019
    Charlie Wells

    Charlie Wells New Member

    Macon
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    I need help wiring the heater switch to the heater motor on my 69. Can anyone help maybe with a diagram? Thanks
     
  2. Oct 15, 2019
    Rick Whitson

    Rick Whitson Detroit Area 2024 Sponsor 2022 Sponsor

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    Welcome from Michigan, I have a 64 CJ so I can't help you with your Jeep, but someone on this site will have what you need, Good Luck
     
  3. Oct 15, 2019
    Twin2

    Twin2 not him 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Virginia Beach, VA
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    three wires on switch
    (1) 12volt hot - switched
    (2) fan motor - low / one wire hot to motor
    (3) fan motor - high / both wires hot to motor
     
  4. Oct 15, 2019
    Charlie Wells

    Charlie Wells New Member

    Macon
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    Thank you sir.
     
  5. Oct 15, 2019
    Charlie Wells

    Charlie Wells New Member

    Macon
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    Thnx
     
  6. Apr 16, 2022
    Eric

    Eric Member

    CA
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    This is an old post so it might get nowhere. Thought I would give it a try, regardless.

    I'm looking for clarification. Two wires come from my heater fan. It is grounded through frame. Applying current to one wire starts fan. Disconnecting first and applying current to the other starts fan at higher speed. I assumed one wire was for low speed and one for high. In this post, it suggests that both wires need to have current applied for the high speed function. Is that correct? (I worry that applying current to both might damage something... but that is my ignorance speaking.) Thank anyone in advance for any insight they can offer.
     
  7. Apr 16, 2022
    skipilot

    skipilot Member

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    I have a ‘69 and it is how you describe, one wire for low speed, one wire for high speed. I’m positive the switch doesn’t connect the two for high speed as my OE switch was missing when I bought the Jeep and I put an aftermarket rotary switch in. Hope this helps.
    Tim
     
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  8. Apr 16, 2022
    Twin2

    Twin2 not him 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    one more time
    fan switch Low - Copy.jpg
    Low - only one terminal Hot

    fan switch High - Copy.jpg

    High - both terminals Hot
     
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  9. Apr 16, 2022
    Eric

    Eric Member

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    They say a "picture is worth a thousand words." I guess they weren't kidding! Thanks. Is it safe to assume that sending power to each circuit in the motor simultaneously does not hurt the motor?

    I was digging via the search function but never came across these photos. Greatly appreciated. And I appreciate Skypilot's comments, too! Would be fun sitting around a bench with some hot coffee and discussing, but this is a close second.
     
  10. Apr 16, 2022
    Eric

    Eric Member

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    Follow-up question: Is there a way to fix this?
    broken switch tabs.jpg
     
  11. Apr 16, 2022
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    I might be able to fix it (not an offer to though). I would have to take it apart and look at the other side of the rivets. Possible you could replace the tabs by using parts from another switch.

    I would spend some time and effort looking for a replacement first.
     
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  12. Apr 16, 2022
    Twin2

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    post a WTB ad in classified section
    seen a few heater control units for sale there . that's where I got the one in photos
    warning . it's like hen's teeth by itself (switch)
    Did take opportune to look at spare fan motor
    one wire it runs on Low
    the other one it runs on High
    now I couldn't tell you if it ran any faster with both
    good luck with search
     
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  13. Apr 16, 2022
    skipilot

    skipilot Member

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    That is very interesting and a great pic. I’m no electrical wiz but my guess is it does not spin faster with just the “high speed” wire connected vs both. I assume the “low speed” goes to some sort of resistor to drop the voltage to the motor and the “high speed” wire gives full voltage. If you can never provide more voltage than full voltage, the motor can’t speed up. I suppose you could put in a 24v system and it would go really fast. Does my thinking make sense? I wonder why they did it that way, there may be a really good reason that my limited electrical knowledge isn’t grasping.

    Tim
     
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  14. Apr 16, 2022
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    Not a resistance change. There is some combination of windings in the motor that changes the field strength. That's how they get a speed change with no change in voltage. Hard to say how the motor is connected internally, since the DC resistances between the windings are so low that a measurement does not tell you anything. The motor has a time-varying impedance (the 'back EMF' or generator output) when it's running that the applied current works against. Different winding configuration changes the back EMF and thereby the motor speed.
     
    Last edited: Apr 16, 2022
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  15. Apr 16, 2022
    skipilot

    skipilot Member

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    I’ll refer back to my “I’m no electrical wiz” statement . Any guess on why they did it the way they did and if there is a benefit to having both wires powered. Mine works well with either one or the other.
    Tim
     
  16. Apr 16, 2022
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    The speed may be the same, maybe not the power. Hard to say without knowing something about the design of the motor. Or possibly the electrical efficiency is higher with both wires powered. I know a little about electricity, not so much about motor design. If your curiosity compels you, learn more about motor design, buy a replacement motor and take it apart to see how its connected. You could figure it out given time and motivation.

    Certainly the main reason is to get two speeds and avoid throwing away a lot of energy as heat (resistance losses). How that's done in this case is the question. I'm sure it was connected this way for some good reason.
     
    Last edited: Apr 16, 2022
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