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need help with charge system

Discussion in 'Diesel Tech / 24 volts' started by attatoy, Feb 28, 2007.

  1. attatoy

    attatoy

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    I have a 81 bj 42, i have had charge issues since i owned this truck(2 weeks), i took the alt off and to the alt shop, they told me the rotor is ****ed, so i happen to locate another one, i instal it and i ave the excact same issue, that is no change in votage from 25 volts till i rev the truck to 2000 ish or more then it goes to 27.25 ish, i have 25 v to the one side of the slip ring from the reg, and have grounded the other, neither has increased the voltage, i am at a loss as to what to replace, as the reg seems to werk to reg voltage at high rpm, as well as turns of voltage to the rotor under key off. I have three wires off the alt, but not the factory plug(someone has changed these, i worrie they are wrong but need to find info to prove what goes where so i do not damage anything( very weiry with sutch a rare alt) any thing you think i can do to porve or confeirm bad parts, the alt shop said the diodes and rectifier where good. i just feel i need more info.

    what kinda resistance should i see though a rotor, i had about 25 k if meory serves, either way it was the same as the other one i just replaced, and they both passed voltage though them.

    Myles
     
  2. Ron R

    Ron R Drive a Landruiser, enjoy life

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    Myles,

    I posted a cutout from the wiring diagram of a 40. It should be identical to your 42 for this part. Hope it's readable enough.
    You can see the alternator and regulator.
    The are connected by four wires.
    Make sure the posts the wires connect to have the same identifiers.
    Furthermore check the condensor. Look what the voltage does when it's disconnected. It's there to suppres voltage spikes so replace it if it's shot.
    Also check connections to ground from the alternator and the engine to chassis.
    alternator bj40.jpg
     
  3. attatoy

    attatoy

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    my only issue is the wires on the alt it self are white, green and blue, white is to slip ring, as well as green id mem servese(i lifeted the brush cover, either way this other wire gets 24 v and the white is the one to the reg i assue, it is heavier then the 24v hot one. the third wire is the one that has me confused, also in your diagram,

    F is Field
    B is what? brush?
    E is what?

    i wish people would not **** with s***. i have been hesitant to change the wires around to try it.
     
  4. Ron R

    Ron R Drive a Landruiser, enjoy life

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    B= Battery (White -light blue)
    E= Exiting (white-black)
    F= Field (white-green)
    N=Neutral?(White- light blue)

    But mind this is from a 40 !! so basicly look at it to compare with your's and to have a schematic view on how it's compiled.
    Make sure all the contacts are clean, if not done yet. Also to ignition and condensator.
    I'm afraid that's all I can say to it.
     
  5. attatoy

    attatoy

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    so if feild is 24v hot, and exciting should be the out of the field(though the rotor) then the b should be though the startor? if this is the case i did not remeber 24v to it, again i will check, this could be my issue. does this sound plausable, ie does exciting come from ther rotor, or is this the stator circute?
     
  6. attatoy

    attatoy

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    lookin for values i should see on each wire, e is to ground, b is to batt voltage, f and n come from the reg and i have no idea what i should see there, i would excpect f to vary voltage to make power in the alt, f goes to ground after does it, or does f return though the neutral to the reg?
     
  7. duckling

    duckling

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    I think the diodes can go bad so the thing will not charge sufficiently. I played with mine, swapping out parts, and even toying with the charge lamp relay. Then I forked over the nearly 400 clams for a new alternator and the problem went away.

    84' BJ60
     
  8. Ron R

    Ron R Drive a Landruiser, enjoy life

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    I'm sorry I don't quite understand what you are trying to tell.
    I'll give it one more try.
    F and E go to the field = stator.
    B = batt should come from the brushes and go to the battery more or less directly.
    On this wire you should find the battery voltage all the time.
    On E and F only when ignition is on.
    During low rev you should see more or less battery voltage, when revs go up and voltage reaches 28,8, the voltage on this connection (E and F) should slowly drop thus regulating voltage and current delevered by the alternator.
     
  9. attatoy

    attatoy

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    i guessi must have a diode problem then , casue i get charging at high rpm, i checked all my wires and all looks good, an i full fielded the alt again, and got nothing, but as i said if i rev it i will see a increase in voltage to opperating voltage, 27. somthing, they where tested by a shop , but i gues si will have to assume they where incorect.
     
  10. Ron R

    Ron R Drive a Landruiser, enjoy life

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    Yes, can be they made a mistake. If you do so, take the regulator as well. Have it checked also.