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Alternator not charging

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  • Alternator not charging

    Well she runs like a top but the alternator isn’t putting out anything. I’ve got a good connection between the alternator charging post and the positive battery post and continuity between the alternator body and the battery negative post. The signal wire connected to the back of the alternator has a voltage of 0.9 which seems odd. Anyone have any ideas? If it wasn’t brand new I’d say it was no good...

  • #2
    Update: After fiddling with the connector on the alternator it came to life. Must have been a bad connection there. All is well!


    • #3
      The small plastic connector with two cavities (only one filled) does not do anything, you will find that the small wire goes to a plug which is not used.

      My alternator is also not charging, which connector did you fiddle with? The charging post one?

      If I did not know better I would also say that my alternator is dead.


      • #4
        How long has it run? The ECM doesn’t command charge until the rpm goes past a point in my experience


        • #5
          Drove about 3 miles today, went from idle to redline.


          • #6
            Yeah I messed with the deutch two pin connector and it seemed to wake it up. I have also watched the murphy gauge at idle and if it idles for a long time it seems to stop charging as RePowerToy said. Seems like a few things went that way, like it needed to be run a few times and put to work before the ECM "wakes up" completely. For instance, I had a bit of trouble with cooling fans not coming on at first but now they work fine.


            • #7
              If anyone is still having problems with this try to run a ground cable from the aluminum alternator case directly to the battery's negative terminal. Also elevating the RPMs slightly above idle might get the alternator off of its lazy ass.

              I bet its all the clear coat they sprayed on the engine thats messing up the ground path, way to go cummins.


              • #8
                Per our specs, the direct alternator ground cable should only be necessary if you have switched to using an aftermarket (aluminium or anodized) alternator bracket. Technically, it's a best practice to ground it directly no matter what.

                Way to go Cummins for high-temp clear coating engines? Our thought in coating our engines is that when you have any aluminum pieces on an engine or machined grey iron surfaces, the clear coat is meant to keep them from oxidizing. Feedback captured though that it's not for everyone!