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  1. #1
    Sr. Apprentice
    Join Date
    Sep 2011
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    Rockwell, North Carolina, United States
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    Exclamation Alternators burning up on my 1985 Silverado

    So Ive restored my 85 chevy back to mostly factory appearing, plus all my customizations. Ever since I have put the truck back together I have had alternator problems, if they're charging they're squeaking, no matter how tight/lose the belt is. If they're not squeaking, they're not charging. Ive even tried a "one wire" alternator and it burned it up. The other day me and a another guy completely went thru all the wiring and found a few problems and straightened a few things up. I got a new alternator to charge and not squeak and then i tied all my wires up and fired it back up and it squeaked, here is what i have found: if i test the regulator(brown/White/keyed power) wire on the alternator while its plugged in to it, it reads 3.15 volts but if you unplug it, it reads 11.57 volts like the rest of the truck. Whats going on here? is something burned up or not right? The alternator screams, is the 3.15 volt wire not allowing the alternator to fully engage hence the squeaking..

    Thanks,

    Royce
    Last edited by Royce Lancaster; 05-29-2012 at 10:39 PM.
    BUILT, NOT BOUGHT
    1985 Chevy Silverado Longbed 4WD
    400 Chevy Small Block/400 Chevy Transmission
    Detroit Lockers Front & Rear/4.10 Gears
    35" BF Goodrich Mud Terrains/6" Rough Country Suspension lift

  2. #2
    Sr. Apprentice
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    Sep 2011
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    Rockwell, North Carolina, United States
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    Default

    Any advice from anyone?

  3. #3

    Default

    Sounds like you may have a wire that has some insulation missing. If it worked while the wiring was loose and down, but not when it's bundled nice would indicate that to me. Just gotta chase down wiring and find the bad wire.
    Christopher

    1991 Chevy Suburban 1/2 ton 2WD w/ chevy SBC 350-3/4 ton drivetrain upgrade w/4.10 gears 200K miles
    2005 Saturn ION-2 Stock 277K miles
    1982 Bronco, 1993 Bronco (sold), 1971 M35A2 Deuce and a Half



    There are 10 kinds of people, those who understand binary, and those who dont...

    Remember kids, the only difference between screwing around and science is writing it down- Adam Savage

  4. #4

    Default

    you have a hot wire grounding check down by the starter make sure there is nothing touching.

  5. #5

    Default

    Let me get this right, you have a 85 Chevy, with a v belt alternator, and the belt squeals when it's charging, but if you tighten up the belt, the alternator still turns but it doesn't work? What I know is this, V belt alternators squeal when the draw or load on the alternator exceeds the belts grip, so the belt squeals due to slip. Is the belt new or old? Has the battery been checked by a GOOD tester? Have you added aftermarket sound, lighting, or anything else that might place more of a load on the electrical system than a stock truck? If so, you may need to add a second alternator and battery to keep up with the load.
    Turn the truck off completely and remove the battery cables from the battery, and check them with a meter to see if you have a leak. Sounds to me like a short somewhere is causing a huge drain on the charging circuit. Have you replaced the main battery cables? Do you mean to say the truck burned up the one wire alternator, or the one wire alternator burned up the belt? What do you mean by this exactly? "
    I got a new alternator to charge and not squeak and then i tied all my wires up and fired it back up and it squeaked,




    Brian Larson CST. KC9DAK.
    Janesville WI.
    87 GMC G20 6.2 diesel.

  6. #6

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    Quote Originally Posted by RallySTX View Post
    Has the battery been checked by a GOOD tester?
    Exactly, this is your problem, you proved it with the "it reads 11.57 volts like the rest of the truck" statement.
    Ray

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

  7. #7
    Sr. Apprentice
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    Rockwell, North Carolina, United States
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    Default

    Quote Originally Posted by RayVoy View Post
    Exactly, this is your problem, you proved it with the "it reads 11.57 volts like the rest of the truck" statement.
    The battery is brand new, just replaced it trying to track this problem down. Cables are fairly new, not worn.

    Quote Originally Posted by RallySTX View Post
    Let me get this right, you have a 85 Chevy, with a v belt alternator, and the belt squeals when it's charging, but if you tighten up the belt, the alternator still turns but it doesn't work? What I know is this, V belt alternators squeal when the draw or load on the alternator exceeds the belts grip, so the belt squeals due to slip. Is the belt new or old? Has the battery been checked by a GOOD tester? Have you added aftermarket sound, lighting, or anything else that might place more of a load on the electrical system than a stock truck? If so, you may need to add a second alternator and battery to keep up with the load.
    Turn the truck off completely and remove the battery cables from the battery, and check them with a meter to see if you have a leak. Sounds to me like a short somewhere is causing a huge drain on the charging circuit. Have you replaced the main battery cables? Do you mean to say the truck burned up the one wire alternator, or the one wire alternator burned up the belt? What do you mean by this exactly? "
    I got a new alternator to charge and not squeak and then i tied all my wires up and fired it back up and it squeaked,
    This was a 78 amp factory style alternator. Yes I have a Sound system but its all on a separate circuit and the alternator still acts the same when it is unplugged.

    Quote Originally Posted by kw70chevy View Post
    you have a hot wire grounding check down by the starter make sure there is nothing touching.
    Second thing I checked.

    Quote Originally Posted by Crawdaddy View Post
    Sounds like you may have a wire that has some insulation missing. If it worked while the wiring was loose and down, but not when it's bundled nice would indicate that to me. Just gotta chase down wiring and find the bad wire.

    As of RIGHT NOW I have fixed this issue with Replacing the Alternator again, so far so good.

  8. #8

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    Quote Originally Posted by Royce Lancaster View Post
    The battery is brand new, just replaced it trying to track this problem down.
    Ok, but a fully charged battery should read 12.5x, not 11.57, was this a typo?

  9. #9
    Sr. Apprentice
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    Rockwell, North Carolina, United States
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    Default

    Quote Originally Posted by RayVoy View Post
    Ok, but a fully charged battery should read 12.5x, not 11.57, was this a typo?
    Its just what the battery was reading at the time, from constantly starting the motor with out the alternator charging, and driving around for a day with out it charging.

  10. #10

    Default

    Yeah, I was afraid of that one, I have had a couple people go through several new alternators before they actually got a good one, that happens. I hope the trouble is fixed.
    Brian L.

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