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Alternator Smoke?

Discussion in 'Intermediate CJ-5/6/7/8' started by B-Rad, Feb 16, 2019.

  1. Feb 16, 2019
    B-Rad

    B-Rad Member

    Dayton
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    Hey everyone, went out to start my jeep( 75 cj5 304) and the battery was dead. I check the battery with my volt meter and it didn't even show 1 volt. Odd, becasue I just ran it a couple weeks ago and used a battery maintainer on it then for the day.

    So I hook up some cables to another battery I have in the garage. Tried to start it and absolutely nothing. Got back out to see smoke coming out of the alternator area. And the wires going from the battery side of the starter solenoid down to the back of the alt. were melting. So I kicked off the cables and it quit smoking.

    Is my alternator internally shorted or something? The battery went completely dead in about 2 weeks. Never had any troubles with the battery.

    Thanks
     
  2. Feb 16, 2019
    Elevatorman

    Elevatorman New Member

    Winchester VA
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    Jan 16, 2019
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    Sounds like the alternator to me. Same very similar thing happened to me on my 79 f250. Alternator actually caught on fire.

    But that’s my only experience, so I hope someone with a little more knowledge on this will chime in soon.
     
  3. Feb 16, 2019
    B-Rad

    B-Rad Member

    Dayton
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    It does have an external voltage regulator, not sure how to test to see if that is ok?
     
  4. Feb 16, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    Yeah, smoke and melted wires is pretty drastic. Do you have the '75 TSM? Cheap, llike $25 on CD-ROM from RockAuto. The '75 circuits are more like '76 than '74, and there is a '76 TSM online here - Jeep® 1976 TSM online The electrical section will have a step-by-step chart for diagnosing charging problems. Likely you'll have to repair/replace the wires and components before you can follow the chart though.

    To help any more, you'll have to show us in a picture or on a diagram which wires melted. Here is a scrap from the '76 CJ diagram:

    upload_2019-2-16_17-34-36.png

    These fusible links are intended to protect the Jeep from the stored energy in the battery in case of a catastrophe. Possible they did their job ... I suggest you compare to the diagram and see what is melted.
     
  5. Feb 16, 2019
    Focker

    Focker That's a terrible idea...What time? Staff Member

    WA
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    What's scary is this could have happened while the Jeep was unattended. This is why I have a battery disconnect switch.

    You should consider installing one.
     
  6. Feb 16, 2019
    B-Rad

    B-Rad Member

    Dayton
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    Yes, I will probably install one.
     
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  7. Feb 16, 2019
    B-Rad

    B-Rad Member

    Dayton
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    Attached Files:

  8. Feb 16, 2019
    B-Rad

    B-Rad Member

    Dayton
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  9. Feb 16, 2019
    B-Rad

    B-Rad Member

    Dayton
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    Ok so, first pictures shows what I think is the voltage regulator.

    Second picture shows where someone has spliced 2 pieces of wire together running from the starter solenoid to the back of the alt.

    Third picture shows the starter solenoid, both the red and blue wires were warm, especially the blue one which turns into the red one in the previous picture that goes down to the alt.

    Fourth pic shows the alt, the red wire at the top is the red wire mentioned above that was spliced to the blue one. It seemed to be the smoke source, was melty looking. The green and black wires with the blue terminal ends iand the wire with the red terminal end i believe go to the regulator. Does it matter which way the two wires with the blues ends go? Can they be reversed without issues? That how i put them back after the motor rebuild last year.
     
  10. Feb 16, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    All those crimp connectors with the blue or yellow insulation are owner mods. I don't know what the big blue wire is - it's has to be a PO (previous owner) mod. The factory alternator feed is red. There is also a big red wire that goes under the dash to feed the rest of the car. When I say "big" that's 10 ga, unlike most of the rest of the car which is 14, 16 or even 18 ga (much smaller wire).

    You have correctly identified the regulator. It has a 4-conductor connector with gray-black-red-yellow on the JEEP side of the plug, not the regulator side. That looks correct and original.

    You need the TSM with the wiring diagram for your year. Wiring of a '75 is completely differnt from previous years, and there were many many changes for the 1976 model year that will affect the wiring. You need a 1975 wiring diagram. Do not buy one of the Haynes or Chiltons manuals for this Jeep ... you need the factory manual. Once you have that, make copies of the wiring diagram and start tracing through the wiring to separate the PO mods from the factory wiring. Enlarged photocopies of the diagram that you can color and make notes on might help you. Sorry, it's very difficult to diagnose electrical problems unless you have the car in front of you... especially when it's been changed from the original wiring.

    You can take heart that 1975 was the first year for a voltmeter, which replaced the ammeter of previous years. This makes the charging circuit a lot simpler and safer. If the PO removed the fusible links and replaced with plain wire, that was a mistake. You need to look for those 14 ga fusible links and make sure they are there.
     
  11. Feb 16, 2019
    B-Rad

    B-Rad Member

    Dayton
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    I have a fsm, guess I'll have to dig in. That blue wire comunc off the starter solenoid turns into that red one that goes down to the alt. So that other red one must go into the dash area.

    It's still odd that something drained the battery all the way to practically nothing.
     
  12. Feb 16, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    The alternator is always connected to the battery. If there is a short in the alternator, it will drain the battery. I have experienced this problem with the later Delco alternators, where the Jeep ran one day and the battery was completely flat in a few days (my J20). Replacing the alternator fixed it. The Motorola alternator is pretty awful by modern standards. In the day, they blew diodes, and the mechanics soldered-in the new diodes. Today, a complete replacement alternator costs less than the repair parts. I still have my original alternator in my CJ-6, but at the first sign of trouble, it gets swapped out for a Delco 10SI with an integral regulator.

    Note that the 6-cylinder 1975 CJs got a Delco, but the V8s got a Motorola... Jeep must have had a huge pile of Motorolas.
     
  13. Feb 17, 2019
    B-Rad

    B-Rad Member

    Dayton
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    Ok did a little more digging in the wiring, its not to hacked up compared to my fsm surprisingly. The inside of the alt you can see wires that use to have a coating on them burnt.

    On the alt how do i know which wire goes to where on the two terminals? I cannot see any markings on them, I am just guessing that i got them on right when i rebuilt the motor?
    IMG_20190217_134553.jpg IMG_20190217_134549.jpg

    Next thing is this (box) it says in the manual its a electronic module or something? THe wires go to the dist, coill, and supposedly the tach, my tach is not stock thats for sure. Is it just a brain for the ign system?

    IMG_20190217_132831.jpg

    Thanks for all the help everyone!
     
  14. Feb 17, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    If you look at the alternator, you will see that one of the tabs is part of the case, and that goes to regulator ground. You have three other wires, the regulator lead, the brush lead, and the output. Look at Fig. 3-7 in your TSM - they are clearly labeled. The harness to the alternator would have had an plastic shell on the end that only fits one way on the pair of terminals. Someone cut it off when they fitted the hardware store crimp connectors.
    Again, you're not referring to the manual. Look at page 3-42. That gold anodized box is the control module for the ignition. It's just a big transistor that turns on and off in response to a low-voltage signal from the distributor. It's also easy to find on the wiring diagram in section A2. Search for "Prestolite ignition" and you'll find dozens of old posts about it.

    The small black cube on the fender is a relay for some accessory. Not Jeep.
     
    Last edited: Feb 17, 2019
  15. Feb 17, 2019
    B-Rad

    B-Rad Member

    Dayton
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    Thanks for the help, I was never good at electrical wiring diagrams.
     
  16. Feb 17, 2019
    3b a runnin

    3b a runnin Active Member 2023 Sponsor 2022 Sponsor

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    ME TOO, and I use them
     
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  17. Feb 17, 2019
    B-Rad

    B-Rad Member

    Dayton
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    Are you running the disconnect on the ground side? Doesn't the alt. have power at all times since the wire runs from the battery to solenoid then down to alt?

    Would it be better to have a disconnect on the power side?
     
  18. Feb 17, 2019
    3b a runnin

    3b a runnin Active Member 2023 Sponsor 2022 Sponsor

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    My disconnects are on the ground side of the battery. That is the way they are intended to be wired. With the ground broken, there is no way for power from the battery to be "hot" anywhere because there is no return connection.
     
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  19. Feb 17, 2019
    Oldriginal86

    Oldriginal86 Member

    Pasadena, Md.
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    I didn’t think it mattered which side of the power circuit is broken. On ALL marine applications its the positive side that the disconnect is installed.
     
  20. Feb 17, 2019
    3b a runnin

    3b a runnin Active Member 2023 Sponsor 2022 Sponsor

    virginia
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    It's not critical to break the neg. side. Most of the battery top disconnects are sized for the neg. post. And less chance of any sparks.
     
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