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negative cable on alternator

This is a discussion on negative cable on alternator within the General Help forums, part of the LSx Technical Help Section category; does there need to be a cable from the negative battery terminal to the back of the alternator??? mine has ...

  1. #1
    caraholic ggino85's Avatar
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    blue green chameleon
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    negative cable on alternator

    does there need to be a cable from the negative battery terminal to the back of the alternator??? mine has one connected on the back with a bolt, doesnt look wright..... is it suppose to be a ground connected to the car somewhere? car is a 95 lt1(far from stock)

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    That guy thearborbarber's Avatar
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    Nope. It grounds through the block which is connected to the neg side of the battery.

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    caraholic ggino85's Avatar
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    blue green chameleon
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    whats connected to the negative side of the battery? the ground for the battery? if so then mine doesnt have that, i think that is wat is connected to the back of the alternator? so could the cable connected to the negative battery terminal and the back of the alternator be the reason on a scanner it shows like my alternator is not fully charging the system or something like that.(tuner said the alternator was weak) its brand new.......thanks for the help

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    That guy thearborbarber's Avatar
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    The negative on the battery goes to the chassis. The block grounds to the chassis. The alternator grounds to the block. The alternator doesnt use any wire to ground the case is its ground.

    I would check both the connections on the battery. Corrosion could cause your battery not to charge. I would take the alternator out and have a parts store check to see if its charging.

    Also what exactly is going on with your car that your asking about the alternator and its ground?

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    caraholic ggino85's Avatar
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    blue green chameleon
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    ok thats kinda wat i thought (the neg cable goes to block not the alternator), the guy that put the outer accessories (alternator, egr, AIR) on the car, did somethings wrong. so im in the process of fixing it. The battery has a cable from the neg terminal to the back of the alternator (held on by a bolt on the bracket), i think this is the ground thats suppose to go into the block. im having a ton of little issues but some that i think the cable on the alternator is causing are; the cluster guages will bounce just a bit with the blinker, the battery test good but when the car is running it will always be a little in the orange on the cluster guage and the alternator is brand new.

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    caraholic ggino85's Avatar
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    blue green chameleon
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    ok im confused......there is a cable from the negative terminal of the battery to the chassis(mine car has that, thats fine) my car also has a cable connected to the negative terminal of the battery thats running to the back of the alternator screwed on with a bolt that holds the alternator on the engine, should this be there?

  7. #7
    Electrical Engineer KMdef9's Avatar
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    Quote Originally Posted by ggino85 View Post
    ok im confused......there is a cable from the negative terminal of the battery to the chassis(mine car has that, thats fine) my car also has a cable connected to the negative terminal of the battery thats running to the back of the alternator screwed on with a bolt that holds the alternator on the engine, should this be there?
    No.

    Both your battery and your alternator and everything else eletrical needs 2 things to complete a circut. A positive feed (+) and a negative feed (-). Negative feeds are also know as commons. When you ground the battery to the chassis, it becomes a common. Since you alternator casing is metal, mounted on a metal bracket, which is mounted to your engine block, which in turn is grounded to the chassis as well, your alternator already has the common/negative feed/(-).

    I would disconnect the wire from your negative terminal and see if that helps. If not, you could ground that wire to the chassis (not in the same place the battery is), b/c it is possible that the alternator is no longer properly grounded. That could be why the installer ran a new ground wire.

    Do you have pics of the setup you could post?

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    caraholic ggino85's Avatar
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    blue green chameleon
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    Quote Originally Posted by KMdef9 View Post
    No.

    Both your battery and your alternator and everything else eletrical needs 2 things to complete a circut. A positive feed (+) and a negative feed (-). Negative feeds are also know as commons. When you ground the battery to the chassis, it becomes a common. Since you alternator casing is metal, mounted on a metal bracket, which is mounted to your engine block, which in turn is grounded to the chassis as well, your alternator already has the common/negative feed/(-).

    I would disconnect the wire from your negative terminal and see if that helps. If not, you could ground that wire to the chassis (not in the same place the battery is), b/c it is possible that the alternator is no longer properly grounded. That could be why the installer ran a new ground wire.

    Do you have pics of the setup you could post?
    i dont have a pic now but i will take one and post it in the morning at like 8am, thanks everyone for your feedback.

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    Electrical Engineer KMdef9's Avatar
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    Never a problem, the more details you can provide, the better/faster we can help.


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