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Pulsating lights

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 89K5guy, Sep 2, 2006.

  1. 89K5guy

    89K5guy 1/2 ton status

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    I asked this question a few months ago with almost no results:confused: My lights (all of them)pulsate,flicker ,whatever you want to call it as soon as I pull them on,whether full headlights or just parking lights.The factory volt gage and a handheld volt meter both show between 13 and 14 volts with engine running.
    Could it be that the alternator isn't supplying enuff amps and causing the pulsating/flickering effect?The alternator looks old and is probably stock or is a replacement with a low amp rating.Any advice would be greatly appreciated.:bow:
     
  2. cbbr

    cbbr 1 ton status GMOTM Winner

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    Take the alternator to Autozone. They will test it for free. You will get more hits on a question like this in the Garage forum.
     
  3. 1985_K5_Silverado

    1985_K5_Silverado 1/2 ton status

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    All of them, head/tail/parking/marker/dome/courtesy/etc? Does it do it less with the engine off? A corroded/oxidized headlight switch could be the culprit, or even just an unreliably semi-conductive hot lead that feeds the switch (making and breaking the contact rapidly, manifested as flickering, with engine vibration). You could check resistance across the switch or see if there is any difference between voltage in and voltage out.

    If you need to change the switch, it's easy to do, but make sure you disconnect the battery main ground cable first before you start poking around under the switch.
     
  4. 88sub4x4

    88sub4x4 1/2 ton status

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    Check the grounding at the alternator, as well as the main grounds off the battery. A simple voltage drop test will reveal if it's OK.
     
  5. Leper

    Leper 1/2 ton status

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    Agreed. Check all grounds. If you hit the brake, does the problem stay the same or get better or worse?
     
  6. 89K5guy

    89K5guy 1/2 ton status

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    The lights don't pulsate/flicker with the engine OFF.Only when running.:confused:
    Alternator problem???
    I am going to clean and sandpaper all the ground connections to the radiator
    support and from the battery to the engine block.All the grounding straps to the firewall are present.Any other ideas?:confused:
     

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