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Wiring-what Does This Do?

Discussion in 'Early CJ5 and CJ6 Tech' started by colojeepguy, Sep 28, 2019.

  1. Sep 28, 2019
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    Looks like a GM a/c compressor connector. Those were set up like that to reduce voltage spikes and backfeeding when the compressor clutch was engaged. Just so happens they were the same dimensionally for many other switches used in Jeeps, like backup light switches. I used one in the daughter’s ‘69 on her T-14 when I rebuilt it. I had to cut apart the connector and remove the diode or resistor, I forget which that one had. I think diode.
     
  2. Sep 28, 2019
    Jw60

    Jw60 Sitting up n buckled down. 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    How are the switches failing? Internal leaks or corrosion on the points? I could see using the switch to signal a relay to reduce wear on the points. That would also prevent the back feed into the switch if used for towing.
     
  3. Sep 28, 2019
    colojeepguy

    colojeepguy Colorado Springs

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    The lights stop working...no contact in the switch. I have used Standard, Delco, and a "low pressure" switch from Painless Wiring. I think now I will cut this plug out and replace it with a standard one...see what happens.
    I also flushed out the brake fluid today, in case there is debris in the system plugging up the switches (it looked pretty clean so I don't think it is an issue).
     
  4. Sep 29, 2019
    zinertia2

    zinertia2 "and which part are you keeping?" 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Suggest someone did this


    upload_2019-9-28_21-56-54.jpeg
     
  5. Sep 29, 2019
    Admiral Cray

    Admiral Cray I want to do this again.. Staff Member

    Bainbridge...
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  6. Sep 29, 2019
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    Tantallon, Nova...
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    65CJ5 SRD and Focker like this.
  7. Sep 29, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    Now that kind of looks like a diode (Doug's pic in post 18). The band would be on the green wire end.
    Yes, that's right - same as what Nick suggests above. You got the commonly used name right. Shorts out the inductive spike from switching a motor or coil or such.
     
  8. Sep 29, 2019
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    Why in the world would someone install that as a connector on a brake light switch?
     
  9. Sep 29, 2019
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

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    Because it fits the silly little studs on the brake switch, the proper female spade connectors are hard to find. That's why I thought it was an alternator plug- well known use in this application.
     
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  10. Sep 29, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    We had a recent thread about this. Hydraulic Brake Light Switch Failure - Again CJMark linked to this interesting post on a Volvo page - SW-EM Hydraulic Brake Light Switch Investigation

    Yes, you could use a relay. The coil of a Bosch-type relay is about 150ma, while the bright filament of an 1157 is 21 watts => 1.6A for each bulb, so a considerable load reduction from the bulbs. The relay coil does have an inductance, so here a snubber would make sense, I'd think. Maybe not needed for such a small coil, but easy to include when you are adding the relay.
     
    Last edited: Sep 29, 2019
    65CJ5 SRD likes this.
  11. Sep 29, 2019
    ITLKSEZ

    ITLKSEZ Hope for the best, prepare for the worst

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    I’m pretty sure we could start a thread similar to the “What is this?” thread called “Why in the world would someone do this?”

    Some of the crazy things I’ve seen in old jeeps over the years... :crazy:
     
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  12. Sep 29, 2019
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    Yep! And it would certainly be an entertaining one. :)(y)
     
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  13. Sep 29, 2019
    Walt Couch

    Walt Couch sidehill Cordele, Ga. 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Yep Nick nailed it.
     
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  14. Sep 29, 2019
    colojeepguy

    colojeepguy Colorado Springs

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    Do you guys think that could be causing my repeated switch failures? I don't see how but I'm no electricity expert....
     
  15. Sep 29, 2019
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

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    I would think not.
     
  16. Sep 29, 2019
    47v6

    47v6 junk wrecker! 2023 Sponsor 2022 Sponsor

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    In this article, SW-EM Hydraulic Brake Light Switch Investigation , it states that the current across the internal contacts causes arcing and failure. If you were to use a low voltage relay ,or even one with a full 12 vdc coil, and use the pressure switch to only fire the coil in the relay to power the full current of the brake lights the pressure switch last longer.

    I would still just wire up a regular switch to run either the full current of the brake light off the brake pedal arm or to fire off the coil of a relay to do it. I was so irritated with the situation that I made sure to pick hanging pedals to eliminate the pressure switch amongst other reasons.
     
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  17. Oct 1, 2019
    65CJ5 SRD

    65CJ5 SRD Member

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    Just a couple of thoughts (take them for what they're worth!!)

    You could go to LED brake/turn lamps to lower the current draw way down. If your brake lights and turn signals use the same lamp (pretty common), you'd need a mechanical flasher in place of the regular one to go LED (you can add a resistor instead but to me that defeats part of the advantage of having LED lamps). I've had a mechanical flasher in my Jeep for a long time, but still have the regular brake/turn lamps in it. For now. I plan to replace them in the near future. Note that with a regular flasher, if one of the regular lamps burns out, it will flash a lot faster than normal (letting you know there's a burned out lamp somewhere). You won't get that with regular lamps and a mechanical flasher. It will always operate at the same rate regardless.
     
  18. Oct 1, 2019
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

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    Honestly a couple of amps should not be burning out contacts within a few months of operation- these things should last for years & years. :( Where are you getting these things from?
     
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  19. Oct 1, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    If the switch contacts are arcing (if that's really the problem), I'd think you could put a capacitor or RC circuit across the switch contacts and prevent arcing that way. This slows the voltage rise/fall across the switch contacts. Supposedly Horowitz&Hill TAOE has a discussion of switching inductive loads which you can look at, or I will look when I get home. If you use a relay, you want a snubber across the relay coil, as shown here.

    upload_2019-10-1_10-55-11.png

    Here the DC load is the relay coil, and the switch is to the left. You can buy relays with diode snubbers built in - mind the polarity.
     
  20. Oct 1, 2019
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    I kind of agree with Howard here...I replaced my brake light switch when I first got my jeep and had to replace the MC, and its never had an issue since. I think I got the common one sold at FLAPS (oriellys specifically - guessing it might be Dorman?). At the same time, I feel Doug's pain, as its my reverse back-up lights switch that are always going bad. I've cooked that switch a few times, and other issues, so I finally put a 15A fuse in the line and its been popping fuses ever since. Its pulling way too much current, but the lights are functional. So, it feel very similar to Doug's issue - which is why is it pulling so much current to be burning the switch up, yet its not shorting to ground before it goes through the lights (as they work)....I realize this isn't a solution, but thought it might give some context....Maybe Doug could measure the current going through the switch when the brakes are applied. Seems to be a similar issue and possible solution for both of us. Is an inline resistor needed to minimize the current flow (granted, it would dim the lights a bit?)
     
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