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94 940 alternator 900

posted by  Andrew Woods on  Fri May 31 16:13 CST 2002
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reposting since I've looked into the problem some more and my last post was pushed way down.

When I turn my car on sometimes the alternator isn't charging. The SRS light will be on because my voltage is low and if I put a load on the alt. the battery supplies the power, the alt just sits there. I have to rev the engine up to 1700 Rpm's or higher before the alternator starts working and the voltage goes up. I can then put a load on the alternator and it will be creating the power, not the battery. The alternator light isn't on when this is happening, maybe it dosen't work since all the warning lights are messed up in my dash, except the SRS and seatbelt lights.

Do I need a new alternator? I have the 100 amp alt and there is a plastic casing on the back, and I've been told that the brushes and voltage regulator are internal and not replaceable. what do I do? new alt?

Thanks! you guys are a big help.
--
My 91 245








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    94 940 alternator 900

    posted by  chris herbst on  Sat Jun 1 03:58 CST 2002
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    last visit: Mon Oct 20 20:32 CST 2014
    [RELATED]

    Do you have the 100amp Bosch or Nippondenso alternator?

    I think the ND has a plastic casing but it's not the kind of thing you can just yank out. If it's a Bosch then just pull the two screws--as said--and put a new brush/regulator unit in.

    But first I'd clear up the warning light issue.
    --
    1992 940 wagon, 72k
    make people envious; smile often.








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    94 940 alternator 900

    uid 5008's pic
    posted by  Colin UK on  Sat Jun 1 00:28 CST 2002
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    Andrew,
    The most likely reason for this behavior is the fact that your alternator light is not working. The alternator gets it`s initial exitation from the warning lamp (but will some times self exite due to residual magnetism at high revs) Try putting a temporary lamp (5W or less) between the large battery cable and the warning light terminal on the back of the alternator.If this works normally and the alternator charges OK then that is your answer.
    Hope this helps, Colin.








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    94 940 alternator 900

    posted by  B.C. on  Fri May 31 17:11 CST 2002
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    last visit: Wed Mar 28 22:28 CST 2012
    [RELATED]

    Your symptoms sound like the brushes are worn far down. The paarts book I have shows your car to have a Bosch 100A unit. If they are like the 80A then the brushes can be replaced.

    The word "internal" may be being used to differentiate from the older external voltage regulators which had a harness from the alternator to a separate unit regulator.

    The Bosch units I know about have a part on the back, held with two machine screws, that is both the brush holder and the voltage regulator. If you can replace that unit with a new one, the problems should be solved.

    Good Luck,

    Bob

    ;>)







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      94 940 alternator 900

      posted by  Andrew Woods on  Sat Jun 1 19:08 CST 2002
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      Yes, I have a Bosch 100 Amp alternator. I'll try to so if I can get to the voltage regulator/brushes. I replaced them on my 240 so I know what to look for.

      I have a feeling that the problem lies within the voltage reg/bruse assembly so I'll swap it out and see what happens. I sure hope it cures the alternator noise in my radio. but it makes it easy to determine weather or not the alternator is working.
      --
      My 91 245







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