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  1. #1
    Jr. Apprentice hihoslva's Avatar
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    Default Voltage gauge issue/question

    I've got a '99 'Burban 1500 2wd - 165,000 miles on the clock.

    I recently swapped out the stock 105 amp alternator for the heavier-duty 140 amp unit, and have a puzzling gauge issue.

    My stock gauge seems to be ultra-sensitive now, as if the calibration is askew. Use of any power accessories (headlights, A/C blower, hell even the directional blinkers) causes a big drop on the gauge.

    But I've tested with a multimeter and find that the actual voltage drops are minimal and totally in the acceptable range.

    For example: Yesterday I was using the full boat of accessories to test things. A/C on (both front and rear blowers on high), headlights on, stereo on, etc. My dash gauge was reading about midway between the center "14" and the "red zone" on the gauge, which would indicate somewhere around, I guess, 12 volts? The needle position would definitely raise concern, put it that way.

    But when tested with a multimeter, I got about 13.5 volts across the battery terminals, and just over 14 volts testing from the negative battery terminal across to the alternator output terminal. Totally within normal range, right?

    Shutting down the accessories brought the gauge back up to just below the 14 mark, which looks like a big gain on the gauge.

    But testing with the multimeter reveals only about a .1 volt gain - minuscule - to about 13.6 across the battery and about 14.1 from negative terminal to alt output lug. Sounds good to me.....

    It's annoying to see the gauge bounce so much, and I know it shouldn't - I mean the thing actually ticks a little like clock's second hand when my blinkers are on.....

    So what gives? Why would my gauge become ultra sensitive?

    For the alternator hookup, I purchased the proper wiring harness (since the 105 amp alt has a different connector) and soldered the new harness to the stock wire (single wire). I used a friend's '99 Burban 2500 with the 454 engine (and 140 amp alt) as a reference for which terminal the wire should connect to and know I have that correct.

    I'm glad to know the electrical system in my truck is not "unstable" and seems to be working perfectly. But I'd like the gauge to read that as well....

    Any thoughts?
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  2. #2
    Sr. Apprentice BadBurban98's Avatar
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    Default

    well when you have all those accessories on the gauge will drop down to 12v what type of turn signal light you have on the truck?
    Burnin' hard, loose, n', clean

  3. #3
    Jr. Apprentice hihoslva's Avatar
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    Default

    Turn signals?

    Everything on the truck is stock except the stereo. But that's not running any external amplifiers - it's just a normal aftermarket CD player.

    The issue is that the GAUGE reads a drop, but the ACTUAL drop is about 1/10th of what the gauge shows. The gauge might show a 1 volt drop, but the actual drop is only 1/10 volt.
    A new take on metal music
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  4. #4
    Sr. Apprentice BadBurban98's Avatar
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    Default

    turns signals as in bulbs...., so everything on the truck is stock.....uh....my fathers 99 hoe had a problem with the fuel gauge and it bounced around like its got a mind of its own this happened after i replaced the sending unit, then i replaced the potentiometer and it stopped bouncing around, it sounds like the potentiometer is going on your volt meter i'd try replacing it
    Burnin' hard, loose, n', clean

  5. #5

    Default

    Quote Originally Posted by BadBurban98 View Post
    well when you have all those accessories on the gauge will drop down to 12v what type of turn signal light you have on the truck?
    Funny you mention that, as when I use my turn signals on my 95 burb the gauge bounces with the blinking of the turn signal...

    Is it the bulbs or the flasher module causing that?
    Last edited by jtwh20; 04-12-2010 at 08:23 AM. Reason: spell
    burbn' in NC

  6. #6
    Jr. Mechanic
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    Jan 2009
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    Elizabeth City, NC
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    Default

    It sounds to me like your guage went south on ya. Sounds like you wired it up just fine and you know your electrical system is just fine. I would either go with a new guage or throw one of those aftermarket plug in deals that goes in the ciggarette lighter port.

  7. #7

    Default

    If I remember correctly, the voltage is read off a lead that attaches directly to the charging terminal on the alternator. Perhaps you have a bad connection there that's causing your issues. Corrosion, partial wire breakage, loose physical connection come to mind. It also makes sense since you were just messing around a good bit in that direct area.
    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 265K miles
    1982 Bronco, 1993 Bronco (sold), 1971 M35A2 Deuce and a Half



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