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Battery/Alternator problem??????

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by gth, Dec 29, 2006.

  1. gth

    gth New Member

    I have a 2000 silverado ext 4x4 5.3l that I have been having a little
    problem with.

    A few days ago I was driving and noticed the battery light come on and
    the volts gauge was reading around 10 -11volts. I turned off all
    accessories and headed her for home.

    Once home I took the battery (delco factory) to Canadian tire for them
    to test it. It tested ""replace". So I did with a new 875cca terminator
    battery. When I installed the new battery the truck started fine but I
    noticed the battery warning light was still on. I let it run for 20min
    or so to see if it would charge. (or what ever was wrong might
    magically fix itself) The light didnt go out so I tried some of the
    accessories to put a load on it. The wipers and blower motor ran but
    noticeably slowly.

    I just decided to let the truck run with all accessories off. The
    battery light didn't go out so after running for 1/2 hour or so I shut
    off the truck and the the battery now shows 11.7V across the terminals.

    I charged the battery back up to show 12.6V across the terminals.

    Then I started the truck and checked the voltage across the terminals
    with the truck running (no access on at all)......11.3V....What
    the.....and the bleeping battery warning light is still on.

    I tried revving the truck to 2000-2200 rpm (no access on at all) and
    the voltage across the battery went up to 11.49 at one point but it
    also fluctuated down to 11.27 also....

    Does this sound like a new alternater to go along with my new
    battery???? What are the odd that both the battery and alternator would
    crap on the same day???

    PS. I have never had another issue with this truck until this
  2. 84fiero123

    84fiero123 Epic Member 5+ Years 1000 Posts Platinum Contributor

    It’s more possible the alternator was the problem and that’s what killed the first battery.

    If it’s not putting out 13 Volts to the battery them the alternator is most likely bad.

    Drive it with no accessories on for 20 min. and if you can find a voltage gauge that just plugs into your cigarette lighter see what that reads at speed.

    But it really sounds to me like your alternator was the real problem that killed the battery.

    Unless you have a bad connection between the battery and ground, at the battery or at the ground.

    Or from the pos. to Starter, check all connections.
  3. gth

    gth New Member

    I had already taken off and cleaned all connections.............looks like I need an alternator. Thanks.
  4. 84fiero123

    84fiero123 Epic Member 5+ Years 1000 Posts Platinum Contributor

    Before you go and just buy a new alt. take it off and have it tested.

    Most parts stores do it for free.
  5. ChevyFan

    ChevyFan Administrator Staff Member 5+ Years 5000 Posts

    I've done that in the past, almost certain that it was an alternator that was going out, but it ended up being some other electronic component.

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