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  1. #1
    Jr. Mechanic dfhollums's Avatar
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    Default Pulsating Lights

    1999 Chevy Suburban, alternator replaced earlier today, and the battery is around a year old. When the lights are on they pulsate, my wife told me that she saw the battery light come on and all the lights dimmed briefly then went back to pulsating when the battery light turned off. All the connections are good, so what could be the problem?

  2. #2

    Default

    Have the battery load tested, also check the battery grounds.
    Then test that new alternator

  3. #3
    Jr. Mechanic dfhollums's Avatar
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    Default

    Thanks for the tips, I will check that out. According to the build code for the alternator for the truck it is supposed to be a 105 amp and that was what I re-installed.

  4. #4

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    check all grounds like said above. Having a bad ground can do some weird stuff to a truck.

  5. #5
    Jr. Engineer poncho62's Avatar
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    Default

    Yup...sure sounds like a bad ground somewhere

    1997 GMC

  6. #6

    Default

    Definitely check all of your grounds. Ensure that when installing the new alternator, the plug going to the regulator didn't get damaged/unplugged. Make sure that the terminal wasn't damaged to the positive post on the alternator, as they can get corroded and become weak. I used to work at auto parts stores and have also seen SEVERAL "new" alternators bad straight out of the box. If everything related to the battery posts, terminals, and ground straps comes back okay, I would suggest that you return the alternator to the store you bought it and demand a replacement (even if it tested "good").

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  7. #7
    Sr. Apprentice
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    Default

    As said previously, have the alternator tested and check your grounds. If you cannot seem to find a bad ground try to reground your alternator to the chassis. Seems to me that one of the windings in your alternator is bad, hence the pulsating effect.

  8. #8

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    Alt! Don't ask how I know.
    2010 GMC SIERRA CREW CAB (Silver) 4x4, ReadyLift 2.5" Level Kit, 305/60/18 Dick Cepek Mud Country, Go Rhino Nerf Bars, Husky Liners front and rear, Bushwacker Bed Rail Caps, Custom tuned. 4:11's

  9. #9
    Jr. Mechanic dfhollums's Avatar
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    Default

    Much obliged for y'all's tips. O'Reilly Auto Parts warranted the alternator, the problem was most likely the internal regulator. I purchased a remanufactured alt. from the Ultima line because of the lifetime warranty, the Best Test version only has a 1 year warranty. Interestingly, I had advise from a counterman that was nearby the one helping me about going with the Best Test alt. over another Ultima version because of bad experiences he had with the Ultima alt., going through three on his vehicle in a months time, but having the "lesser" alt. in his vehicle for almost a year. He told me he'd give a week on me installing another alt. like the one I had before I'd be back again. I went with the Best Test alternator. Any others of y'all had similar problems with the Ultima line of hard parts from O'Reilly Auto Parts?

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