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  1. #1

    Default runs good, except with lights on

    i have a 1994 chev with a 305.
    it starts and runs fine but turn on the lights and it starts to run "rough", turn them off, runs fine.
    if i turn on the emergency flashers it will "miss" every time they flash.
    Then if i step on the brakes it will completely die.

    any ideas what could be wrong?

  2. #2


    Sounds like a charging system issue. I had a 2003 yukon xl with a bad battery and alternator. When I would stop at a light it would almost stall. Let my foot off the brake and it was fine. I installed a new battery and alternator and it corrected the issue.

    1995 Silverado 4x4
    6" BDS Suspension Lift-3" Body Lift-Add A Leaf in rear -Trailmaster SSV Shocks-Duel Steering Stabilizer Kit -AirAid Cold air intake-
    4.56 Gears with Detroit Auburn Locker-Pro-Comp Traction Bars with duel shocks-Aluminum Skid Plate Kit-38.5" x 16.5" Mickey Thompson Baja Claws-Constant Dropping fuel gauge

    2005 Yukon XL Jet Power Programmer, Bilstein Shocks, Bilstein rear springs, Helwig Anti-sway bars, EGR Window Visors, EGR Hood Shield, Denali Headlights, Headlight harness upgrade, GE NightHawk Bulbs, White Night Rear lighting system, Russell Braided SS brake lines, PowerStop Brake pads, PowerStop cross drilled and Slotted Rotors,
    2002 Silverado ext cab 2wd (Sold)
    2003 Yukon XL (Totaled)

  3. #3

    Enkeiavalanche's Avatar
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    Get them tested If you don't have what is needed go to a pep boys
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  4. #4


    I agree with the guys, that it sounds like a battery that won't hold a charge, or an alternator that won't charge the battery. But, the lights don't use a lot of power and it seems you are using so much of the available power that there isn't enough remaining to keep the plugs firing. A battery needs to be pretty low before that becomes a problem.

    How does it start, does the battery spin the starter with sufficient power?

    I agree with the guys you need to have the battery and alternator tested, but you may need to check/clean/replace some of the ground cables.

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

  5. #5


    Replaced alternator today and Battery is new within the last 3 months.
    issues remain the same.
    starts and runs but turn on lights on touch brakes then dies, but will restart right away.

    Am i going to be chasing a bare wire somewhere in the harness?
    Last edited by gord19; 12-14-2013 at 05:42 PM.

  6. #6


    Just because the battery is fairly new, doesn't mean it can't have an issue. I'm with the rest of the guys. Have it tested. Then start looking for a short somewhere that is dragging both the battery and alternator down when you turn on the lights.
    Myself, my beautiful wife
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  7. #7


    Nothing wrong with getting the battery tested, it's a good place to have started, but a quick backyard check is to answer my previous question.
    Quote Originally Posted by RayVoy View Post
    How does it start, does the battery spin the starter with sufficient power?
    If it spins the engine (no dragging and slowing down) the battery is probably fine. And if the battery is fine, the old alt was working because it kept the battery charged.

    As I suggested in my earlier post, you probably have a bad ground wire, or a bad ground connection.

    Quote Originally Posted by RayVoy View Post
    but you may need to check/clean/replace some of the ground cables.

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