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twitching voltmeter

This is a discussion on twitching voltmeter within the Technical / Maintenance forums, part of the General Discussion category; When starting cold, for the first few minutes, my voltmeter occasionally dips for a split second from 14 or so ...

  1. #1
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    twitching voltmeter


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    When starting cold, for the first few minutes, my voltmeter occasionally dips for a split second from 14 or so volts down to about 12 for maybe a split second. It's probably right because the lights also dim. As the truck warms up, it goes away. I get this reading from an aftermarket gauge. The stock gauge is still hooked up, but responds too slowly to read the "twitching." Probably an alternator problem. Does anybody know what part of the alternator could be causing the problem?

    93 RCLB with "Remy New" alternator replaced about 40000 miles ago.

  2. #2
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    Re: twitching voltmeter

    I would check your connections at your battery gauge also take a regular volt meter and go arcoss the battery and see what volatge reading you get on start up and see if the same problem ecurs on the hand held voltmeter

  3. #3
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    Re: twitching voltmeter

    loose positive wire to alternator, loose/bad engine ground(s), or a broken wire (inside the red insulation) going to the voltage regulator (the 4-prong plug on the alternator), or a bent pin on the 4-pin harness, or maybe a cold cracked solder joint on the voltage regulator.

    How many miles? The brushes (and/or slip ring) could be at end of life.

    Bad diode(s) will show up when everything is warm at low rpm (450-550)
    Last edited by helo; 03-30-2011 at 06:38 AM.

  4. #4
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    Re: twitching voltmeter

    The truck has 218,000 miles on it. I replaced the alternator with a "remy new" alternator from advance auto parts about 4 years ago. I noticed a wire coming off the positive terminal of the battery to accessories (an amp) was still connected, but in pretty bad shape. I'll fix it this weekend. I've also seen many posts on "the big three" upgrades that include replacing the battery to alternator wire with a thicker cable along with battery to ground. I thought of trying that before looking at the alternator.

  5. #5
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    Re: twitching voltmeter

    Ah, I missed the last line in first post.

    Replacing all the big cables isn't a bad idea if you have extra 2ga-4ga wire sitting around, but it's not really worth the expense if you don't have a subwoofer or other high drain accessories. At least disconnect all the grounds and sand/grind on all the contact points so everything is shiny when you bolt up the ring terminals.

 

 

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