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sparking alternator

Discussion in 'Technical Q&A' started by atlantaman, Apr 8, 2004.

  1. atlantaman

    atlantaman Formula 3

    Mar 31, 2002
    1,726
    Roswell, Georgia
    Full Name:
    Charles
    Although i know a lot about 308 and 330 motors from working on mine a lot--i am not a evpert on alternators and this thing i saw tonight is baffeling me.

    the story:

    1) take a working 328 alternator to a local shop and tell them that I need more power. I have EFI and HID lighting which sucks power.
    2) They install a mercedes core and say that I now have 104 amps--cooool!

    3) tonight I pull into my garage and was looking at the motor while it was running--someone recently asked me if my headers glowed at all at night so I was lookng at them in the dark.

    then i noticed it---i very slight flash from the alternator---when I run up the PRM to about 4000--the alternator sparks madly from top and bottom. At first I thought the pulley was rubbing something--but no--it is definately electrical.

    any ideas? why is this thing discharging all over the mounting bracket and what causes this?

    needless to say it is coming out tomorrow--dont like having sparks that clost to the gas
     
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  3. Verell

    Verell F1 Veteran
    Consultant Owner

    May 5, 2001
    6,993
    Groton, MA
    Full Name:
    Verell Boaen
    That's really wierd. Any chance you could get a pix of the sparking. The brushes in the back will naturally spark a bit under load, especially when they're new & haven't worn in.

    However it sounds like you're getting sparks from the mounting bracket?

    Hmm, The alternator is grounded by the tensioning bracket as I recall. I sort of remember the pivot mounts being rubber, hence non-conductive. If the tensioning bolt is a little loose you might get sparks under vy high current.
     
  4. atlantaman

    atlantaman Formula 3

    Mar 31, 2002
    1,726
    Roswell, Georgia
    Full Name:
    Charles
    the sparking is centered about the top mounting bracket. It is secure too. I am thinking that the regulator may have dumped on me--OR-- that the mercedes cors installed is for a much slower RPM design (ie--bigger pulley wheel) and it is over spinning.
    Anyway--it is definatley not mechanical failure since there is no noise coming from it.
     
  5. Verell

    Verell F1 Veteran
    Consultant Owner

    May 5, 2001
    6,993
    Groton, MA
    Full Name:
    Verell Boaen
    It sounds like the alternator case is just not adequately 'grounded' to the engine. ie: The full return current is trying to go thru the upper mounting bracket/bolt & there's too much resistance, or else the path is making/breaking under vibration. (By the 'upper bracket' I assume you mean the slotted one you use to adj belt tension. Check the pivot point for the bracket to see how it gets to the engine. Perhaps the pivot bolt is slightly loose?

    Pull the alternator & take a vy good look at the mechanical path that electrically connects the alt. case to the block. Sounds like something may be feeling mechanically tight, but isn't making a vy good elec. connection.
     
  6. ham308

    ham308 Formula Junior

    Nov 3, 2003
    358
    NE Switzerland
    Full Name:
    Richard Ham
    Please don't forget to tell us what the fix is.

    Definitely wierd.....
     
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  8. WaltP

    WaltP Formula 3

    Nov 1, 2003
    1,465
    Cape Canaveral/Atlanta
    Full Name:
    Walt P
    Did the headers have a glow to them? Thanks, Walt
     
  9. Auraraptor

    Auraraptor F1 World Champ
    Lifetime Rossa Owner

    Sep 25, 2002
    11,441
    MO
  10. atlantaman

    atlantaman Formula 3

    Mar 31, 2002
    1,726
    Roswell, Georgia
    Full Name:
    Charles
    walt--the headers were not glowing----lol

    I discovered that the upper mount was broken--thus not grounding the unit completely--I had to remove it and weld it back together

    I have not gotten the alternator tested yet but will next week--had to pull my motor out due to serious oil consumption--6 qts in 500 miles--think 3-4 exhaust guides are worn bad
     

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