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  • Alternator and Voltage Regulator

    What a great source of info. I've been reading and studying for a while. This is my first post. I am a hobbyist-- not a pro. I have a '74 Scout II project that needs a ton of work. The goal is an overlander/mall crawler. I have pretty much decided to swap in an R2.8 and AX15. Still up in the air on the transfer case. I haven't purchased this stuff yet, but doing some planning.

    Finding that my stock wiring is crumbling, hacked up, and not a great configuration to begin with (specifically, the use of an amp meter), I landed on the below.

    http://www.madelectrical.com/electri...p-gauges.shtml

    I plan to remedy this with a new wiring harness when I get to that point. In reading a bunch of other stuff on that site, I learned a few concepts that I would like to implement in my build. Although this is geared for older cars, I would think the concepts still hold. The below is a long read, but part 3 (through the links) shows what he recommends for remote voltage sensing and alternator-to-battery charging.

    http://www.madelectrical.com/electri...evymain1.shtml

    Questions:
    * I assume the system voltage is read by the ECM. And that it is controlled via a lighter gauge wire from the ECM to the alternator (somewhere I saw a second wire to the ALT in a picture or something). Does anyone know where in the system that voltage is measured? The guy above says that measuring it at the alternator can give lower readings, thus the alternator doesn't put out enough volts to match the actual load, which can lead to lower voltage across the entire system.
    * The guy above also stresses that the alternator runs the electrical system and the output should be sent to a distribution bus first. Off that bus are the feeds for the system and a separate battery charging wire. Benefits are slower battery charging, cleaner battery posts, etc. Is it possible to break from the wiring scheme outlined in the installation manual and use the distribution bus/charging wire in lieu of running the ALT-out straight to the Battery-POS? The ECM and starter/ALT not sharing a ground is no problem to do.

    Thanks in advance for any guidance. It's going to be a while, but I look forward to getting the ol' girl up and running on diesel.

  • #2
    I can't wait to see your Scout project. I suck at electrical so I'm not going to chime in, but I've been having issues with my aux battery not being charged so I'm going to watch this thread to see if maybe there's something going on with the alternator that's causing this issue. My charge controller keeps saying it's working correctly, but it never charges my aux battery, even with solar.

    Anyway, have you looked at the TR-4050? Unless size is an issue, I kinda think the gearing would be awesome with the R2.8 and unless you're gonna go with something like an Atlas, I would think the Dana 300 would be a really good case. Can you fit a doubler?

    My biggest issue I've had with my Jeep is the gearing, I'm only going to be drop my gear ratio to 3.73 at the axles going from 3.07s and my first gear is only 3.83 and the NP-231 is only 2.72. The gearing of the TR-4050, with appropriate axle ratios would have you taking off in second gear without touching the accelerator and 3rd gear is at a pretty good spot and then 4th and 5th are practically the same as the AX-15. If you were going off-road with a Dana 300 with 4:1 and the 6.11 first gear and maybe 3.73s (depending on tires, but I'm going with ~ a 33" tire), you'll have a good crawl ratio too.In 4x4 Hi in first gear, you'll have a great speed for many trails.

    Just something to consider. I would have swapped over, but being in such a short wheelbase, with extended range fuel tank and wanting to add to my lift, as well as doing a tummy tuck, length is my enemy and the TR-4050, seems to be longer than the AX-15 from the few specs I've seen, though it would be doable, I think it's more trouble than it's worth for me to go back, but maybe after I get my Atlas 2, I'll reconsider.

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    • #3
      Originally posted by Rob View Post
      What a great source of info. I've been reading and studying for a while. This is my first post. I am a hobbyist-- not a pro. I have a '74 Scout II project that needs a ton of work. The goal is an overlander/mall crawler. I have pretty much decided to swap in an R2.8 and AX15. Still up in the air on the transfer case. I haven't purchased this stuff yet, but doing some planning.

      Finding that my stock wiring is crumbling, hacked up, and not a great configuration to begin with (specifically, the use of an amp meter), I landed on the below.

      http://www.madelectrical.com/electri...p-gauges.shtml

      I plan to remedy this with a new wiring harness when I get to that point. In reading a bunch of other stuff on that site, I learned a few concepts that I would like to implement in my build. Although this is geared for older cars, I would think the concepts still hold. The below is a long read, but part 3 (through the links) shows what he recommends for remote voltage sensing and alternator-to-battery charging.

      http://www.madelectrical.com/electri...evymain1.shtml

      Questions:
      * I assume the system voltage is read by the ECM. And that it is controlled via a lighter gauge wire from the ECM to the alternator (somewhere I saw a second wire to the ALT in a picture or something). Does anyone know where in the system that voltage is measured? The guy above says that measuring it at the alternator can give lower readings, thus the alternator doesn't put out enough volts to match the actual load, which can lead to lower voltage across the entire system.
      * The guy above also stresses that the alternator runs the electrical system and the output should be sent to a distribution bus first. Off that bus are the feeds for the system and a separate battery charging wire. Benefits are slower battery charging, cleaner battery posts, etc. Is it possible to break from the wiring scheme outlined in the installation manual and use the distribution bus/charging wire in lieu of running the ALT-out straight to the Battery-POS? The ECM and starter/ALT not sharing a ground is no problem to do.

      Thanks in advance for any guidance. It's going to be a while, but I look forward to getting the ol' girl up and running on diesel.
      Welcome!! And glad it has been a good source of info, I started it with that intent!

      As for the question I think I understand what you are asking. There is no issue running the alternator to a distribution point then to the battery, I have done this before without any issue. Be careful with grounding to avoid ground loops but that’s common. The ECM logs voltage from the input power wire for the computer I believe but I would have to dig in to see if that’s the case. What is the reason for an amp gauge? (Or volt gauge)

      Again welcome and cheers

      Comment


      • #4
        DieselJeep - Like most Scouts, mine has a bunch of rust. It is going to keep me busy for a while. I have a build thread on a Binder forum. I did look at the 4050, but was a little scared off by the granny gear and the higher price tag. I won't be doing any hardcore wheeling with it and want my soon-to-be driving kids to have an easier time with it. Seems weird to say given that I cut my teeth on a three-on-the-tree. I do like the higher torque specs though. I was leaning toward the Atlas II-- way overkill, I know. I like the D300, but I figured I'd have to find a junkyard/used one and rebuild it. With all of the other work that I have to do, I was trying to buy a plug and play drivetrain. Else I won't have this thing done until 2035.

        Repower - Thank you for the info. I may have dreamed the second wire to the alternator. The pictures in the installation manual look like just one wire. Maybe it has an internal regulator? Or, is there some other way that the ECM talks to the alternator? I think no matter how it is, tying the alternator and ECM to the distribution buss will get the power reading as close to the power generation as I can.

        At any rate, I have been working on a wiring schematic to give me something to follow while building and to document what is there for the next owner (hopefully one of my kids). I'll try to attach what I have now. Still lots of figuring and work to finish it. I have to figure out wire gauges, colors, maybe fusible links/breakers, and such. Note that I was thinking of running a starter relay so that the starter wire is only live when cranking.
        Attached Files

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        • #5
          The R2.8 alternator is internally regulated. The harness on the back simply is a jumper with the other end being on a loose plug intended for OE integration. It would be how you would drive a battery warning lamp for a key on but no charge scenario. Some of the higher amp aftermarket ones (like those used with the Premier Power Welder) are externally regulated.

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          • #6
            Sanders, I currently have a premier power welder on my 4.0 in my TJ. Does Cummins have a spec for an externally regulated 200 amp alternator that would work with my power welder box and fit the mount on the R2.8? My R2.8 was due to show up at my work address yesterday, but I needed a mental health day to look for elk sheds in the mountains, LOL.

            Comment


            • #7
              I ended up sending the cummins R2.8 alternator to premier power welder and they replaced the diodes in it with heavy duty Bosch diodes and set it up to run with my power welder that uses an external regulator. I should have it back in the next couple of days. Greg told me that my 120 amp cummins alternator put out 150 amps when he tested it, so I should be good to go.

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