Alternator Cable Size?

Discussion in 'Marine Electrical / Electronics' started by ArchHibb, May 25, 2018.

  1. ArchHibb

    ArchHibb Captain

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    I searched, but didn't find an answer.

    I discovered the cable between my alternator and the battery charging system has developed corrosion and consequently melted the jacket at the alternator connection. It's a 2 AWG marine cable, CAT 3116, standard-output alternator I believe.

    Should I replace in-like-kind or upsize? Any advice appreciated!
     

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  2. Lobster.mike

    Lobster.mike Senior Member

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    I'm no electrical wizard but it sure seems big enough. Was there any kink or loose connection before it melted?
     
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  3. Keelboater

    Keelboater Captain

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    If it's long enough, cut it back past the corrosion and see how it looks. If it's good, put a new terminal on it and some heat shrink tube.
     
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  4. ArchHibb

    ArchHibb Captain

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    No kink, but I did discover the terminal stud on the alternator had some black material caked around it. My best guess is that it was belt dust that accumulated over time and started to degrade the electrical connection. Once started, heat build up could become an issue and then the cable jacket degrades. Salt air corrodes the exposed copper... you see where this is headed.
     
  5. BlueMack

    BlueMack Senior Member

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    2 awg is plenty big enough, my question is, is that marine wire or welding cable? The first picture, the strands look too fine to be marine wire, looks more like welding cable.
     
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  6. powderpro

    powderpro Captain

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    I also have 2 gauge on my new 6.8L Deere, I would say you're good to go with the size wire you have.
     
  7. Kodiakan

    Kodiakan Senior Member

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    I'd replace it but that's just me. When one end fails who knows what is under the insulation. I've seen a lot of wires that look fine on the outside but had rotten spots.
     
  8. ArchHibb

    ArchHibb Captain

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    Thanks to everyone for the replies. I replaced it with a new 2 AWG marine battery cable from Ancor and will try to find or make a dust shield for the terminal connection.
     
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  9. Toolate

    Toolate Captain

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    I have what looks to be the same alt and its output is 105A and mine is wired with 2/0 also.
     
  10. TCL

    TCL Senior Member

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    Are you sure that the nut at the alternator fitting didn't come loose? That could cause heat, but just the presence of belt dust unless it was between the faces of the fitting would not cause heat.

    I had a similar problem on a battery terminal that was a little loose.
     
    TCL,
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  11. ArchHibb

    ArchHibb Captain

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    Yes, the nut & washers were tight, but all the threads on the terminal, save those covered by the nut, were full of black which I suspect was belt dust. So the cable to terminal contact was definitely compromised.

    I’ll keep an eye on it and see how it goes.
     
  12. Genius

    Genius Captain

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    was the nut a nylock?
     
  13. ArchHibb

    ArchHibb Captain

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    It is now. Regular nut on there had lock washer but was incorrect size; a bit too big. Found a new correct size nut, but only available in stainless as a nylock.
     
  14. Genius

    Genius Captain

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    I'd suggest you go back to a regular nut and lock washer. I've only had problems with nylocks on terminal connections. I really don't have a theory on it, just bad luck.
     
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  15. ArchHibb

    ArchHibb Captain

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    Had a feeling you were going to say that... :confused:

    Cat used a reg. nut & lock washer, so that’s what I’ll use too.
     
  16. captjohn

    captjohn Captain

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    Corrosion, or a loose connection, causes resistance in the wire, and a voltage drop. The resistance results in localized heating of the affected area, if bad enough, yea, it'll melt the insulation. Replacing the wire really is the best answer. Make sure the crimps on the wire ends are nice and tight, or you'll be back where you started from. A mechanic showed me years ago a really simple way to test a wire that you suspect is bad. Using an old fashioned test light, connect it at both ends of the suspect wire. A wire with no resistance in it will have no voltage drop across it, and the light will not come on at all, indicating that the wire is good. But if the wire has resistance in it, resulting in a voltage drop, the light will start to glow, indicating that it is no good and must be replaced.
     

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