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Replacing Battery Cables

Discussion in 'The Garage' started by BlahBlah, Feb 18, 2006.

  1. BlahBlah

    BlahBlah Registered Member

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    I've got a 78 k20 that I just bought a winch for. So I went out and bought a new 140 amp alternator. My question is should I just replace the two wires coming off the battery or should I upgrade the smaller one that goes from the alternator to the starter to? Also whats the difference between a 1 wire and a 3 wire alternator?
     
  2. driney

    driney 1/2 ton status Premium Member

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    Here is some interesting reading on alternators.
     
  3. HarryH3

    HarryH3 1 ton status Author

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    As I recall, the highest output alternator offered by the factory in '78 was a whopping 63 amps. :rolleyes: GM sized the charging wire from the alternator to the starter post accordingly. To keep the charging wire from melting when the new 140 amp alternator goes into full charge mode, you definitely need to increase the size of that wire consierably. :eek1: To handle that much current, you need to use at least a 4 gauge wire.
     
    Last edited: Feb 19, 2006
  4. onetonbb74

    onetonbb74 1/2 ton status

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    a 3 wire has 3 wires: Big red Hot, exciter (usually white), and hot jumper(post to terminal). 1 wire alternator has only the hot wire going straight to the post on the back. If I were you, id run 4 guage straight to the starter from the alternator, and 2 guage from the batterey to the starter. Also a 2 guage ground to the block from batterey.
     
  5. BlahBlah

    BlahBlah Registered Member

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    Thats pretty much what I was thinking. I even bought some 4 guage for that purpose, but do you think I should leave the old wire and add a new one? Or should I rip out the original, too?
     
  6. onetonbb74

    onetonbb74 1/2 ton status

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    just hook the old wire to the junction block on the firewall
     
  7. 84gmcjimmy

    84gmcjimmy 1 ton status

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    hijack:
    anyone know the size of alternator that came in a 84 blazer/jimmy from the factory?

    hijack off
     
  8. HarryH3

    HarryH3 1 ton status Author

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    If it's got a V-belt, then it's most likely a 63 amp model. :(
     
  9. HarryH3

    HarryH3 1 ton status Author

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    I would remove the old one. The insulation on it has probably seen better days anyway. It gets really brittle down where it passes by the exhaust.
     
  10. 4xcrazy

    4xcrazy 3/4 ton status

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    thought they had 78 amp models in the 84 some-odd years?
     
  11. HarryH3

    HarryH3 1 ton status Author

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    I just did some quick poking around at www.partsamerica.com and found a 78 amp AND a 108 amp unit listed as available for a diesel powered '84 Suburban. The 108 amp unit is listed for under $100. Not a bad upgrade for the V-belt set! :cool1:

    However, they don't list the 108 amp unit as being available from AC Delco, so perhaps it wasn't a factory option? :confused:
     
  12. 1985_K5_Silverado

    1985_K5_Silverado 1/2 ton status

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    Not positive about '84, but the optional alternator that's originally was on miy '85 when it rolled out of Flint was the RPO K81 66-amp. Believe it or not, the standard alt on the gasoline models was a 37-amp job! Diesels had the 66 amper as standard equipment.
     
  13. BlahBlah

    BlahBlah Registered Member

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    Thanks guys! I got it all done. I know I should pull out all the original wire and add new stuff in, but that will give me a project for later.
     
  14. 84gmcjimmy

    84gmcjimmy 1 ton status

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    Wow I sure hope mines not a 37 amp one. :eek1:
     
  15. K5er4Life

    K5er4Life 1/2 ton status

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    Theres alot of good info on that site, good post.
     

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