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F134 Starter Switch

Discussion in 'Early CJ5 and CJ6 Tech' started by Don X, Sep 12, 2021.

  1. Sep 13, 2021
    Howard Eisenhauer

    Howard Eisenhauer Super Moderator Staff Member

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    A high resistance connection feeding an open switch as measured with a voltmeter will show battery voltage, but as soon as the switch closes & current wants to flow all the voltage drop will be across the bad connection., i.e you're losing the whole 24 volts in the microscopically thin oxide layer between the lug and the post. And that thin layer with essentially all the power being dissipated in it gets really, really, hot.
     
  2. Sep 13, 2021
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    I'm thinking if that connection got that hot wouldn't there be a noticeable smell? I'm still leaning towards the switch but if not it then is it possible the engine isn't grounded?
     
  3. Sep 14, 2021
    amboynut

    amboynut New Member

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    Clamp one end of a jumper cable onto the negative end of the battery pair and the other end to the starter case or engine block.
    Press the plunger. Report.
     
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  4. Sep 14, 2021
    Dave Deyton

    Dave Deyton Member

    Fuquay-Varina, NC
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    On the WillysMJeeps forum, there is a post on cleaning the contacts in the switch on the starter.
    Just replaced the starter on the 64 M38A1. What a job! No room for a wrench. I still have to get spark, but now the starter turns the engine over. Seems troubleshooting electrical on the 24V system adds another whole dimension.
    Thread on problems with the starter switch:

    Willys M Jeeps Forums-viewtopic-starter switch




    Dave
     
  5. Sep 20, 2021
    Don X

    Don X The Prodigal Moderator Staff Member 2021 Sponsor 2020 Sponsor

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    I tried jumping the terminals on the switch (see pic). All I got was sparks.

    I guess I'll take it apart again and try to clean it more. Failing that I'll have to buy a new one.

    upload_2021-9-20_11-58-4.png
     
  6. Sep 20, 2021
    Glenn

    Glenn Kinda grumpy old man Staff Member

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    Did you only momentarily touch/jump across it?
     
  7. Sep 20, 2021
    Don X

    Don X The Prodigal Moderator Staff Member 2021 Sponsor 2020 Sponsor

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    Yes. By the amount of sparks it didn't look good.
     
  8. Sep 20, 2021
    Glenn

    Glenn Kinda grumpy old man Staff Member

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    Sparks would be expected of course, but you established that the switch is the culprit.
     
  9. Sep 20, 2021
    Don X

    Don X The Prodigal Moderator Staff Member 2021 Sponsor 2020 Sponsor

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    Explain please.

    The sparks were more than what I would expect (1 or 2 sparks when connecting) a hot lead.

    Specifically why?
     
  10. Sep 20, 2021
    Twin2

    Twin2 not him 2021 Sponsor 2020 Sponsor

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    starter motor locked up . yep you'll see sparks . but it should have turned
    pull it and test motor alone
     
  11. Sep 20, 2021
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2021 Sponsor 2020 Sponsor

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    Did you jump it very firmly and without fear? If so, the starter should have spun - if it is good.

    But a timid touch will give sparks and maybe not really test the starter
     
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  12. Sep 20, 2021
    Glenn

    Glenn Kinda grumpy old man Staff Member

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    It certainly could be.
     
  13. Sep 20, 2021
    Glenn

    Glenn Kinda grumpy old man Staff Member

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    This is what I first interpreted his reply meant.
     
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  14. Sep 20, 2021
    Don X

    Don X The Prodigal Moderator Staff Member 2021 Sponsor 2020 Sponsor

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    Okay. Next weekend I'll hook up the jumper with the battery disconnected and then hook up the battery. That should be an easier process with less timidity.
     
  15. Sep 20, 2021
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2021 Sponsor 2020 Sponsor

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    Don't gotta disconnect nuttin'.

    Take an ordinary jumper cable, clamp one end firmly to the starter terminal. Hit the other end hard onto the battery positive post. Starter should crank. Pro Tip - have the transmission in neutral.

    EDIT - See safety comment by 45es, below.
     
    Last edited: Sep 20, 2021
  16. Sep 20, 2021
    45es

    45es Member 2021 Sponsor 2020 Sponsor

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    Reverse this procedure so that you 1) Take an ordinary jumper cable, clamp one end firmly to the battery positive post. 2) Hit the other end hard onto the starter terminal. Starter should crank. The reason is, lead acid batteries emit a explosive gas and you do not want sparks near the battery. This usually occurs when a batteries are being charged but I have seen a battery explode doing just as PeteL suggests.
     
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  17. Sep 20, 2021
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2021 Sponsor 2020 Sponsor

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    Fair point. Rare but possible.
     
  18. Sep 20, 2021
    Alan28

    Alan28 Well-Known Member 2021 Sponsor 2020 Sponsor

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    I used to test with a 2 nd external battery or 2 for 24 volts and disconnect all from the car so I avoided problems and was in the exact subject of testing.
    It takes time, need extra batteries, old ones for ex, cables ...
     
  19. Sep 21, 2021
    amboynut

    amboynut New Member

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    24 volts will make a lot of really big sparks! You can easily weld with 24 volts.
     
  20. Sep 21, 2021
    Glenn

    Glenn Kinda grumpy old man Staff Member

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    This is why I suggested a test light. Not enough current to make a spark.
     
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