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Alternator swap resistor question... UPDATE!

Discussion in 'The Garage' started by Thumper, May 17, 2004.

  1. Thumper

    Thumper 1/2 ton status

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    Ok, heres what Ive done. I swapped my old alternator for the newer style. I changed the pulley to a v-belt, and made brackets for it. Then I bought the adapter harness from GM to adapt the plugs to fit. Now, it wont charge... no output. So, doing some searches, I figure I need a 'resistive wire' in the system because my truck has a volt guage rather than an idiot light. So, the question is: Can a guy just install a light into that wire to make things work? Because the way I understand it, the harness you buy just has a resistor in the wire right? So if I have the non-resistor harness, can I just add a resistor or lamp in the line and make it the same? If so, which wire is it? The smaller of the two or the larger one? Also, what size lamp or resistor is needed?

    Thanks!

    Mike

    Heres the update:
    I figured out why things werent charging, I had wired in a audio amp thru a 50A fuse and a fuseblock. Not sure why, but I wired my charge wire thru the block as well... needless to say, the fuse was roasted as soon as I started the truck. I rewired the charge wire to the battery, and voila... it works! No resistor in the exciter wire, nothing except the basic plug and play type adapter harness.
    To review... heres what I have now: 85 K5, with a new CS style alternator (not sure of the p/n, all the labels are gone except one that says Delco 100A), with a Delco pigtail p/n 12083462 to adapt the 2 wire std plug to the 4 pin plug on the CS style. I replaced the pulley with the v-belt pulley from my other alternator, made up a slightly different bracket setup, and it all works. The battery voltage guage in my dash works as usual, although it is charging at a full 14+ volts /forums/images/graemlins/smile.gif. First time in a long time its charging good. Now for the test... run the winch and see if she can keep up better than the stock 65A unit!
    I will let you know!
    Thanks for all the input guys.
    Mike
     
  2. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    Re: Alternator swap resistor question

    Why don't you want to use the resistor wire harness? If you need the part number, I've got that. It's what I used.

    Aside from that I suppose it would work. I think (guessing) it would be the smaller wire, this is the ignition wire that activates the alternator. The larger wire comes from a battery source.

    Coinsidently, when I did the same install on my truck I used the resistor wire harness and my alternator wasn't charging. My problem was the dual battery isolator. It worked fine when I bypassed that. I think the higher rated alternator fried the isolator.
     
  3. 79Jimmy

    79Jimmy 1/2 ton status

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    Re: Alternator swap resistor question

    I just did the same thing. I put a cs-144 140A alternator in my 79, which also has a volt guage. I didn't need a resistor or light, works just like the old one just ALOT more output particularly at idle. I made my adapter with parts I got from Crappy Tire. Does your 85 use the same 3 wire hookup as the 79? One main which bolts to the back and goes to the battery or starter solinoid and a 2 wire plugin, one being red (thicker) and the other black(?) and thinner. What kind of alternator did you put in cs 130, cs 130d, cs 144.....?

    James
     
  4. Thumper

    Thumper 1/2 ton status

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    Re: Alternator swap resistor question

    Well, as for why I didnt use the other harness... I messed up and ordered the wrong one. After getting hosed 39.00CDN for it, I am not buying another one.
    The isolator thing kinda has me thinkin tho... I believe mine is only 75A, and the alt is 100A. Maybe she pooched.
    Ya, the alt was a 3 wire unit. I read one post from a while ago, and the guy said he had a bulb in it, but it wasnt enough resistance to let it work, but them an 1157 bulb worked. I dunno... Id like to know the actual resistance value for the wire and I will just put one in.

    Anyways, thanks for the input... anyone else?

    Mike
     
  5. Blue85

    Blue85 Troll Premium Member

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    Re: Alternator swap resistor question

    I don't think you need a resistor to make it charge. There is the output, a sense wire and the idiot light wire. Which one is not connected to anything? How do you know there is no output? Are you using a voltmeter or ammeter?
     
  6. Thumper

    Thumper 1/2 ton status

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    Re: Alternator swap resistor question

    Hey, you said you used the resistive harness... can you tell which wire the resistor is in? Maybe you could disconnect it and give it a multimeter reading on both wires and post them up? That would be great!

    Mike
     
  7. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    Re: Alternator swap resistor question

    It's the smaller wire, and it should be 35ohms or more.

    This is the website where I got my info. http://www.novaresource.org/alternator.htm

    I'll get the ohm reading for you as soon as I can.
     
  8. Thumper

    Thumper 1/2 ton status

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    Re: Alternator swap resistor question

    Ok, that would be cool. If I can just toss in a resistor of between 35 and 350 ohms, that would be great.
    Thanks a lot.
    Mike
     
  9. 79Jimmy

    79Jimmy 1/2 ton status

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    Re: Alternator swap resistor question

    Hey Mike if you're running an isolator I would look at that first. I'm using a Hellroaring setup. Like I said I didn't need any resistors or bulbs and mine works flawlessly so far(about a month and a half). Have you put a meter on the alternator to verify no output?
    /forums/images/graemlins/ears.gif

    James
     
  10. Thumper

    Thumper 1/2 ton status

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    Re: Alternator swap resistor question

    I havent directly, but my battery guage in the cab shows battery voltage, around 12-13V. It doesnt change from key on not running to truck running.
    I will definately check out the isolator, hopefully thats it!
    Thanks
    Mike
     
  11. Thumper

    Thumper 1/2 ton status

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    Main post is updated!

    Mike
     
  12. 79Jimmy

    79Jimmy 1/2 ton status

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    Glad to hear you found the problem. I knew it had to be something simple. You'll love the higher ouput at idle but if your winching a lot don't forget to upgrade the wiring, its a must with the 20 year old stock 10 or 12awg charge wire. With the adapter now you can carry the stock alternator, which are a dime a dozen, as a trail spare. /forums/images/graemlins/thumb.gif

    James
     
  13. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    Don't you love it when a plan comes together?! /forums/images/graemlins/woot.gif

    Glad you got it fixed. /forums/images/graemlins/waytogo.gif

    Yea, I agree on the charge wire. That link I gave you earlier recommends 8ga wire, which is what I did.
     
  14. Thumper

    Thumper 1/2 ton status

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    Ya, I have already upgraded my charge wire when I did the isolator mod. I am running 8 guage wires already. I just drove the truck home from work about 10 minutes ago, and WOW. My overhead lights have never been so bright. With my headlights on high beams, and two 130W KCs on, the voltage guage dropped from 14 to about 13.5. With two more 100W KCs on, it dropped to around 12V, but just a 100RPM increase and it jumped right back up to 14V. I love it... long overdue.
    Thanks for all the help.

    Later
    Mike
     

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