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is it true...

Discussion in 'The Garage' started by eightyone, May 13, 2004.

  1. eightyone

    eightyone 1/2 ton status

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    is it true that if you take the positive batery wire off while your truck is running, that it should keep running if the alternator works. and it dies if the alternator doesnt work? and if not, how do i tell if my alternators working corectly? and how do i hook up a voltmeter? sorry for all the questions, but i want to make sure my alternator is doing its job. thanks. /forums/images/graemlins/1zhelp.gif
     
  2. big jimmy 91

    big jimmy 91 1/2 ton status

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    On older vehicles it will show you if the alt. is working by disconecting the battery (negative), I'm not sure about the newer comp. ones though.
    I'm not sure how to formally test the alt. /forums/images/graemlins/thumb.gif
     
  3. heavy4x4

    heavy4x4 1/2 ton status

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    If you don't have the tools or know-how, I think you can drive over to an Autozone and they'll come out and test your alternator.
     
  4. BlazerGuy

    BlazerGuy 3/4 ton status

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    If your alt isn't working you could just disconnect the battery and it'll probably die, it's not really a good idea though. Have you been having problems with a dead battery?
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    Good way to destroy a good alternator. IIRC its the diode trio you kill by doing this "test".

    Turn all of the accessories on (heat on high, headlights, etc.) Run a voltmeter lead from the single red wire on the back of the alternator (if 3 wire setup) and put the other lead to a good ground. That will show the alternator output. If it's above 12V with a high load, at idle, you are fine.
     
  6. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    If you disconnect the battery while the truck is running you could possibly wreck the alternator if it was good in the first place. I've started up a car, removed the battery completely and drove it like that just to get it from one place to another in a pinch. It ran fine and I taped up the battery leads...but it was a $200 car I didn't care about.

    Another hillbilly way to test if an alt is working...if it's working it's creating a bit of magnetism at the pulley. If you're careful you can use a screwdriver near the alt pulley while it's running, if it's working it'll draw the tip of the screwdriver towards itself. Not an especially safe way to test an alt...but I've done it a few times. The center of the pulley is the safest, but even safer is to use a multi-meter.


    [ QUOTE ]
    and how do i hook up a voltmeter?

    [/ QUOTE ]

    With the truck not running touch the black lead to negative on the battery, red lead to positive and note the reading. It should be 12.7-13.0 volts. Start the truck, test the voltage at the battery again...hook the leads up the same way as before and the voltage should read 13.4-14.8 volts or so. If the numbers are higher than when it isn't running the alt is working.

    Rene
     
  7. Z3PR

    Z3PR Banned

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    [ QUOTE ]
    Another hillbilly way to test if an alt is working...if it's working it's creating a bit of magnetism at the pulley. If you're careful you can use a screwdriver near the alt pulley while it's running, if it's working it'll draw the tip of the screwdriver towards itself. Not an especially safe way to test an alt...but I've done it a few times. The center of the pulley is the safest, but even safer is to use a multi-meter.

    [/ QUOTE ] Much safer to do that test off the barring located in the center of the back half of the alt. /forums/images/graemlins/deal.gif
     
  8. 87BrnRsd

    87BrnRsd 1/2 ton status

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    Take your truck to autozone or any car parts store for that matter, and they will test your alternator for free. /forums/images/graemlins/thumb.gif
    -Harrison
     
  9. eightyone

    eightyone 1/2 ton status

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    i havent been having trouble witht he batterey...i just rewired the truck, and want to make sure the alternator is wired correctly, i pulled the negative and it died, then i used the voltmeter and it didnt show any difference. and when i asked how to hook up a voltmeter, i meant ampmeter or watever that gage is that tells if the bateries good...thanks for the help. /forums/images/graemlins/thumb.gif
     
  10. k20

    k20 3/4 ton status

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    yeh ive done that one more than once, never to the pulley though, always to the round piece in the back.
     

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