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Timothy Heck Posted on May 10, 2014
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My alternator is not charging my battery, and both the aternator and battery are brand new and tested positive on the bench tests... Any ideas?

I keep having a problem with my car dying while driving. The battery just runs out of power. It will hold a charge over night, over weeks even, but as soon as I start driving, it eventually will die while I am driving and my battery will be completely dead. I purchased a new alternator and battery and had them both bench tested before installing however im not getting any electricity from the alternator to the battery.

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Jeff3fg

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  • Expert 124 Answers
  • Posted on May 10, 2014
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Could be possible that the bench test was insufficient and read a false positive. More than likely a wire didn't get plugged in, or a connector had a rubber or plastic boot covering the metal, so when it was connected there was no electrical connectivity. There should be a large wire and a small wire coming from the alternator. If you have a multimeter(volt meter) check the voltage when the car is running. Should read about 14.8 volts, 12.6 from the battery and 2.2 from the alternator.

  • 2 more comments 
  • desertracer May 10, 2014

    If the altenator is puting out correct voltage and its not getting to the battery there

  • desertracer May 10, 2014

    wirring problem. see my original answer.

  • Timothy Heck
    Timothy Heck May 10, 2014

    The multimeter read 10.2 on battery and instantly started decreasing. and i tried it at the alternator post and got nothing at all.

  • desertracer May 11, 2014

    The two small wires in the alternator plug are the wires that "excite" the alternator.. This is for the built in regulator to know how much load is on the battery and how hard it has to harge the battery. The wire yyou are concerned with is the one held on by the small nut.Look at the wires in the plug.. just to make sure they are not broken.

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  • Posted on May 10, 2014
 doicarey
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What kinda car do you have? You may have a main fuse blown, check your fuse box, should be pretty big amp fuse like 60 or so. It may locate on the battery post.

  • 2 more comments 
  • desertracer May 10, 2014

    I don' think tis cr has a "main" fues. t does have fuseablelinks by the atarter but if a link was broken the lght owould be on.

  • desertracer May 10, 2014

    I think faster than i Type. I actually had this pronblem and a GM engineer gave me the guage 10wire idea for a 1979 Olds 98 and it fixed the probem.

  • doicarey May 11, 2014

    if you have a alternator likehttp://www.amazon.com/Remy-91312-100%25-...

  • doicarey May 11, 2014

    look at the 3rd picture, there is a positive cable hook up with nut on it, that is the output back to your battery, you should see 13 and half to 14 and half from the nut when running.

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The early GM products would build up restance in the wire that went from the alternator to the starter. The easy cure for this is to install a 10 guage wire directly from the Alternator Batt. lug directly to the battery postive post. Do this using the correct end connectors.. do not just wrap the wire around the termanel. This was a big problem on these cars. especially the Diesel cars. Always disconnect the battery ground terminal before you work on this.

  • 3 more comments 
  • Timothy Heck
    Timothy Heck May 10, 2014

    I don't see the wire from the alternator to the starter, just from the battery to the starter... Is it the smaller wires that plug into the alternator?

  • desertracer May 10, 2014

    The Alternator has a Batt wire on it usuall connected to the alternator with a small nut and many times there will be a red plastic or rubber guard on it. look harder. .. it goes into the harness and ends up at the starter. this is how the charge gets from the alternator to the battery.

  • Timothy Heck
    Timothy Heck May 10, 2014

    i know the wire you are speaking of. it is connected to the alternator with a small nut and connects to the battery. then there are two other wires that go out of the alternator, they are in the plug that plugs into the alternator, is this the wire you are speaking of?

  • Timothy Heck
    Timothy Heck May 10, 2014

    I also converted it from a side post to a top post... the three positive wires are connected to a top post female end with bolts that pull them in tight(if you understand what I mean? sorry hard to describe... coiuld this be the problem?)

  • desertracer May 11, 2014

    in my openion the top posts are far superior to the side posts. I read that you tried to check the alternator out put The engine must be running for the alternator to have any out put.. check it with the engine running.. if the alternator is putting out and the battery is not getting the current then my first post is probably your answer.

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