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Alternator charging question.

Discussion in 'Chevy Trucks' started by 70monte, Sep 4, 2009.

  1. 70monte

    70monte Senior Member
    Messages: 468

    I may have an alternator charging problem on my 98 K3500 but I'm not sure. I was using a used 124a alternator on the truck because the original 124a was making a lot of noise. The used alternator would start out reading over 14v on the gauge and then go below as the truck warmed up. My scanner showed it was only putting out 13.3 volts. I found a good deal on a remanufactured AC-Delco 120a alternator awhile back and bought it in case the used one went out.

    I put the reman one on the other day and its doing the same thing as the used one did although it doesn't go as far below the 14 mark as the used one did. I'm thinking I might have a ground problem but I'm not sure. The battery is brand new as well as the positive side bolt and all battey connections are clean and tight.

    I traced the negative side cable down to where it bolts to the block. It looked clean but I went to take it off and I can't get the nuts off. It has the battery cable on the stud and then a nut and then another wire and then another nut. When I tried taking off the outer nut, the whole stud turned. I can't get another wrench on the inner nut because of the larger connections on the end of both wires that are attached. I tried some needle nose vice grips on the inner nut but that didn't work. I did spray the stud and nuts down with battery terminal cleaner and CRC Freeze off but

    Does anyone have any ideas on getting this loose?

    Is this the main grounding area for the charging system or is there somewhere else I need to look at.

    Does this sound like a ground issue or something else. Thanks for any ideas.

  2. plowinginma

    plowinginma Senior Member
    from MA
    Messages: 326

    You could always ground it somewhere else if you needed too... I run 200 amp in all my trucks.. with 1000 amp batteries..

    Don't trust the gauge either.. use a meter ... you may be OK..
  3. 70monte

    70monte Senior Member
    Messages: 468

    Well, I would have to get it off the stud first to put it somewhere else or cut it and then replace the cable. I still would have to do something with the other cable thats on the stud.

  4. 70monte

    70monte Senior Member
    Messages: 468

    I finally got the stud out. I was able to back it out with the smaller wire still attached. The big ground wire from the battery came loose so the stud just spun in the middle of the end of it. I had to use vice grips and a long breaker bar to get the nut off and free the smaller wire. What I thought was a second nut was part of the stud.

    Now to find a new stud and nut. Both parts stores that were still open did not carry anything that would work. I'm going to try one more place and then the dealer.

    So, does anyone know if this grounding point is the main point for grounding the charging system? Thanks.

  5. brad96z28

    brad96z28 PlowSite.com Addict
    Messages: 1,526

    Did u try a volt / ohm meter instead of reading it on the scanner just to make sure it is actually what it says it?What is the voltage when u put loads on the charging system? Have u cked the amp output? That sounds like that is the main ground that comes from the battery.
  6. 70monte

    70monte Senior Member
    Messages: 468

    I have not tried any of those things yet. I was first trying to make sure all the ground and power connections were clean and tight. The original, the used, and now this new reman alternator were all doing the same thing in regards to the gauge readings. The first two alternators also showed low voltage on my scanner. I have not tested the new one yet. I figured I had a ground or connection problem. I had to order a new ground stud from the dealer since I kind of messed it up taking it out. It won't be in until the middle of next week. I will see what happens after I get the new ground stud in and will do these tests then. Thanks for the help.