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Sparks coming from Alternator when starting.

Discussion in 'The Garage' started by JK5, Oct 16, 2005.

  1. JK5

    JK5 1/2 ton status GMOTM Winner

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    On my 77 K5...

    Everytime I try starting the truck...I get sparks shooting from the Alternator.
    I've never seen this before...is it a short in the alternator??? :(

    Anyone have any experiance with this???
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I'd guess that sparks from an alt would be a short of some sort...have you tried blowing it out with compressed air? We have an old 7" grinder at work that'll spit green sparks out of it once in a while, but a quick shot of compressed air fixes it every time. :dunno: I'm guessing as the brushes wear it ends up with a carbon dust trail inside somewhere. Maybe your alt is doing the same thing?


    Rene
     
  3. JK5

    JK5 1/2 ton status GMOTM Winner

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    Good idea. :D :D

    It's kinda weird...the starter doesn't want to crank at first either.
    I did a load test on the battery...all is well.
    I'll try blowing out that alternator next.
     
  4. diesel4me

    diesel4me 1 ton status Premium Member

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    how's the stud??

    The stud on the back of the altenator,the one the thick red wire goes on,might be loose where it connects insde the altenator..its pretty easy to overtorque the nut and make the stud lossen up inside..just a thought..I think it screws right into the rectifier dewhicky- :confused: -been awhile since I had one apart...at any rate you'd have to open it up to see or fix it..easier to get another altenator.... It might throw sparks if the main output wire is rubbed thru to ground somewhere too,and shorting out intermittently..

    Rene could be right too,I had a generator in a 56 Chevy pickup that looked like an arc welder when the motor was runing! :eek1: --I sprayed a can of "Electri-Motive" spray CRC makes (its like brake cleaner for electric motors and switches)--it stopped sparking after that..but I'd go easy on it in an altenator,it might wash the grease out of the bearings! :doah: :crazy:
     
  5. JK5

    JK5 1/2 ton status GMOTM Winner

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    Thanks...I was hoping you'd chime in. :D

    I'll check that too.
     
  6. bobalob

    bobalob 1/2 ton status

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    The post was my problem little plastic insulating washers had deteriated and allowed post charge to arc occasionally and that eventually melted the rest away resulting in mini welder and then eventually dead battery. stuck some more plastic in, glob of rtv, and tightened post. Also just the nut on the post being a bit loose will let it move internally and periodically ground itself.
     
  7. JK5

    JK5 1/2 ton status GMOTM Winner

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    Thanks for the replies guys!!! :bow: :bow:

    I took off the altenator and replaced it with one I had sitting around from EDdaTree's old k5. Problem sovled!!!! :D :D

    I took problem altenator apart...sure enough...the insulator was split..causing my problems. :doah:
     

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