New alternator wont charge

Discussion in 'Domestics' started by GMC guy, Oct 1, 2017.

  1. GMC guy

    GMC guy Hero Member

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    Please fill out the following to ask a question.

    Pontiac
    Montana
    2008
    180
    3.9

    Van stopped charging. Replaced battery with new one. Still no charge. Installed new alternator. Still no charge. Need help!
     
  2. kev2

    kev2 wrench

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    A 2008 Montana - Not showing up on quick search?
    Maybe add engine size, 3.5 or 3.9, three wires I think - 1 big red to starter with fusible link, a 2 wire connector (gray and orange) to PCM these 2 should set a code if open.
    1. Did you check fusible links, wiring etc?
     
  3. Mobile Dan

    Mobile Dan wrench

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  4. GMC guy

    GMC guy Hero Member

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    It says 3.9
     
  5. kev2

    kev2 wrench

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    I would check fusible link, Info on the battery current sensor later, but I doubt that as it would set codes - did you scan?

    otherwise same as dans 3 wires to alt
     

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  6. nickb2

    nickb2 Wrench. I help when I can

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    Ok, since I like to be the a hole of this site, hello to all BTW I have been very busy lately, not much time to come in here and there,

    Doesn't the PCM have a data line / bus to excite the field? Normally, if I am looking correctly at the wiring that Dan gave, there is a symbol that looks alot like two arrows goings cross current. That normally indicate serial bus line communication.

    So, unless I am wrong, which I am often able to do so, no amount of new batteries or new al;ternators will fix this if the PCM is not communicating in serial data bus line. So Maybe one thing to possibly check out, may have a bad PCM.
     
  7. nickb2

    nickb2 Wrench. I help when I can

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    Ok, well took the time to check, my wiring differs a bit from dans, but still confirms ECM controlled F current. All done by serial data line.

    So unless I have to go back to school, this is a ECM controlled charging system. See black on white PDF ace 0.
     

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  8. nickb2

    nickb2 Wrench. I help when I can

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    So to get ahead of myself, this is the type of situation where a scope shines cuz it will show on a pin test if you have lane to lane switching to excite the generator.
     
  9. kev2

    kev2 wrench

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    I do not think this is a data line, as GM uses a symbol* to ID the CAN lines -

    highlighted in red, the bracket around 'twisted pairs' of can system lines and the diamond are specific
     

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  10. nickb2

    nickb2 Wrench. I help when I can

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    Ok, since I like to debate, what is CAN line? It is a serial bus line. Same thing right? So if the internal voltage regulator in the PCM/ECM does not see what it is programmed to see, no amount of new batteries or alternators will charge since the ECM is not asking to do so. And from what I understand from serial BUS line, it is just a two way street of a pulse that can be measured. Normally in a sine wave of some sort.

    So me going back to school, yes the diamond shape is representative of serial data line. You can also see that the the prefix UE. But the figure you pasted Kev2 is not the one that is for this car.

    But you are right at the same time. So, this is why we have U codes, which are always serial miscommunication codes.
     
  11. nickb2

    nickb2 Wrench. I help when I can

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    But since I just came back from radiology, my head space may be wrong, but I assume we are pretty much saying the same thing, but as usual, my french is getting in the way. But after some research, I am sure this will be cleared up shortly, especially if Billr chimes if he wants. He is the better half of what I try to say here sometimes. @kev2, you are the other half.

     
  12. kev2

    kev2 wrench

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    We are on same page - I was confirming that the wires to alt were not CAN, BUS, DATA -

    Diagram was a random sample to show the symbols for can, bus circuits...

    radiology? You doing OK ? PM me
     
  13. big al

    big al Hero Member

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    Personally, i would do a easy and quick back probe the alt wires and see if gets signal to (turn on) if it does check the large wire on both ends (have found this wire corroded at terminal end and broken, also have seen the fusible link toasted also. If its not getting signal to (turn on) youll need to un wrap the harness and trace back to the splice connector (have seen it break here also but normally on older vehicals)
     
  14. nickb2

    nickb2 Wrench. I help when I can

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    Something wrong with my lungs. I went for blood samples, lets just hope it's some bull shyte cancer thing that can be erased with some magic thinking, I don't have time for that noiselessness.
     
  15. billr

    billr wrench Staff Member

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    I can't be of any help here. Once the simple two-transistor VR regulators were replaced with PCM/BCM control via serial com I lost all interest.
     

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