Voltage meter fluctuation with turn signals?

Discussion in 'Audio & Electronics' started by derekjl, Jan 9, 2018.

  1. derekjl

    derekjl Full Access Member

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    Just installed a brand new alternator on my 1995 Tahoe, AC Delco 100 amp. It’s possible I didn’t notice with the old one, but the voltage meter does move slightly back and forth with the rhythm of the turn signal. Is this considered normal? The only other time I notice it dipping lower than 14 volts is when the rear defroster is on, that seems to suck the most power from it for some reason. Video attached. Some people may not even notice it. Thanks ahead of time!




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    Last edited: Jan 9, 2018
  2. east302

    east302 Full Access Member

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    Check the alternator output (or battery) with the engine running and turn signal on. It should be around 14V.

    The gauge may not be accurate. Mine does this twitching with the signal, too, and the gauge is off by several volts. It's kind of just for decoration now.
     
    Last edited: Jan 9, 2018
  3. william quirk

    william quirk Full Access Member

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    i had the same problem with my 2002 yukon and it was the cluster that was bad i changed out so much stuff before turn signal switch alternator boards relays and the cluster was the bad item ......The cluster repair place i used said they have seen this a few times and couldnt tell me the reason why
     
  4. derekjl

    derekjl Full Access Member

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    Well the thing is it ONLY started happening after the new alternator was installed. But, I guess it is possible I didn't notice it before. It is a very, very small fluctuation as you can see. I've seen some that bounce all around like crazy.
     
  5. derekjl

    derekjl Full Access Member

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    What do you suggest I use as a tester? I do have a real voltmeter with probes, etc. Should I just hook that up to the battery and check the reading? Truck running or off? I'm guessing I could just do something like this video shows. I'll run the turn signals and see if in fact the voltage goes up and down.

     
    Last edited: Jan 9, 2018
  6. east302

    east302 Full Access Member

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    Yep, a cheap multimeter will do the trick. Put one probe on the post at the back of the alternator and the other on battery negative. With engine on, it should be over 14V.

    You can do it from battery positive to battery negative as well like he did in the video. There should be very minimal voltage difference between taking it from there versus at the alternator connection if your alternator cable good.

     
    Last edited: Jan 9, 2018
  7. east302

    east302 Full Access Member

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    The only reason I noticed it on mine was when I drove it after reading your post. It varies about one tick mark per click of the turn signal.
     
  8. derekjl

    derekjl Full Access Member

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    Yep. Exactly the same here. You have to look really close to see it move.
     
  9. Galante

    Galante Elite Member Supporting Member

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    I had a bunch of older gm vehicles that did this. I think grounds and age if vehicle has a lot to do with it.
     
  10. derekjl

    derekjl Full Access Member

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    Well at least everything is working again. I swear the truck feels like it has more power now, like the old alternator was "lagging it down" for lack of a better term. With the headlights and blower motor on it would barely crack 12 volts. It finally shit the bed the other night and drained the battery. I replaced it, the fuel filter while I was at it, and the drive belt. Feels night and day now.
     
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