Alternator Upgrade Question

Mar 16, 2018 4:26 PM - 583 Views Create A New Thread

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GeneF

Pickerington, OH



I want to upgrade my 3-wire Chevy alternator to a one wire unit.
I want to upgrade my 3-wire Chevy alternator to a one wire unit. Was noticing in the new Speedway Motors catalog (pg 202) that they sell a "engine run-on eliminator alt pigtail. One of the bullet points indicates; Special diode prevents engine run-on so you do not have to upgrade to a more modern igntion switch when upgrading to an alternator- plug and play". I never heard of such a thing, and how does this affect the ignition switch (not the key, but the actual switch).? A little background here wil be hlpful, so don't be shy about giving info on this.





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Comments
  • SAM1951
    Mar 21, 2018 at 7:48 PM


  • OK depends on how its wired. older key switches will tie fan circuit and ignition together and even with the required relay you WILL need the diode to keep back feed into ignition.
    might want to check out what im saying with someone else on here.
    good luck
    sam

  • GeneF
    Mar 21, 2018 at 6:10 PM


  • I called Speedway today, and they looked through their technical info. They said that you DO NOT need this if you have a one wire alternator.

    SAM1951, thats a good point. I know if you put a fan on a car, without a relay the wind will turn the blade, and make the LED dash light glow, even when turned off. FYI: I don't do work like that. I had a car once I put a fan on without the relay, just untill I could drive it a bit, for diagnostic purposes.

  • SAM1951
    Mar 20, 2018 at 9:38 PM


  • an electric fan will continue to turn after the engine is turned off.
    the fan will generate enough electricity to keep the ignition hot and the engine will continue to run.
    the extra wiring harness will have a diode to stop back flow into the ignition.
    im sure this is what you are talking about when you use a one wire alternator.
    its a very simple job to change to a one wire.
    go ahead and do this
    make sure the big wire from alternator to the starter is large enough for the load and size of your alternator.
    im sure they will supply you with all the info you will need to do this.
    sam

  • GeneF
    Mar 18, 2018 at 5:39 PM


  • Will, I can't see the photo, I guess it did not post. I envision that I'll end up cutting out the old wires and then ordering a new 140A one wire unit. I'll also run a new heavy duty wire from that terminal on the back of the alternator, back down to the solenoid. The device I asked about...I'm surprised that with all the people on here that I did not get more responses. It's not like I'm the first guy to want to change my system over to the 1-wire unit.... I guess I just won't get an answer to that one.

    Will, thank you for the reply. That's what this forum is all about, people tyrying to help each other.

  • will547
    Mar 18, 2018 at 8:13 AM


  • Not sure about that. I have installed new wiring harnesses in several old cars with the three wire system. The new pig tail has two wires one wire is the exciter and the other ties into the positive wire that runs to the alternator. Here is a photo of how it is wired.

  • will547
    Mar 17, 2018 at 8:04 PM


  • Not sure about that. I have installed new wiring harnesses in several old cars with the three wire system. The new pig tail has two wires one wire is the exciter and the other ties into the positive wire that runs to the alternator. Here is a photo of how it is wired.



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