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need help with flickering headlights!!!

Discussion in 'GM Electrical Tech' started by redneckarmyMP, Aug 30, 2012.

  1. redneckarmyMP

    redneckarmyMP New Member

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    Hey guys, I recently noticed my headlights and dash lights flickering while im driving down the road. I dont really have a lot of electrical accessories in the truck. I have HIDs for low beams, stock high beams and (4) Hella lights on the brush guard which i do not run often. I have also noticed the interior lights dim and voltmeter drop from 14 to about 9 when I roll my windows up.

    Just trying to get an idea of where to start before I start throwing money into it. Im not sure when the battery was replaced but I put a new alternator on it less than 2 months ago. Help! This is driving me crazy! Thanks!!
    #1
  2. SurrealOne

    SurrealOne Former Member

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    Is it only while driving or does it manifest at idle, too? How about if you're parked but applying throttle?

    I'm asking because if it's only while driving it suggests a loose connection ... whereas if it does it at idle or while revving and stopped it could be the alternator.

    I'd certainly check the alternator, engine ground, and battery connections (including the red positive junction box near the alternator) and make sure they are all clean and tight, just for good measure -- regardless of the moving/non-moving bit. If all connections were tight I'd next apply a meter to the alternator if I could reproduce the problem while not moving ... and make sure it's output was consistent.

    Hopefully those basics help...
    Last edited: Aug 30, 2012
    #2
  3. Skippy

    Skippy New Member

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    If you can't find the failure point, just tell people its a safety feature, when you sell the vehicle. People notice you better with flickering lights. LOL

    -Skippy
    #3
  4. moogvo

    moogvo Moderator

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    Check the small ground wire that goes from the negative battery terminal to the body of the truck. That is most commonly the failure that will cause that to happen. If that is secure, move on to other grounds. you have a bad one someplace.
    #4
  5. dobey

    dobey Member

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    You installed HID bulbs in the factory reflector housings? Did you use a cheap 55w HID kit with the big ballasts? I bet if you plug the factory bulbs back in and take the HID stuff out, it will stop flickering. It's a common problem with many HID installs.
    #5
  6. redneckarmyMP

    redneckarmyMP New Member

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    It does it at idle as well as driving. It begins as soon as i start the truck. The HIDs have been in since 2007 so I dont really suspect them. Especially since its not only the headlights that flicker. My interior cab lights, as well as the intrument cluster and radio flicker. As far as I can tell, nothing in particular causes it as far as idle, higher RPMs, in gear or park. The fact that my voltmeter drops considerably while trying rolling up or down my windows makes me think it may be time for a new battery? I suppose it definitely wouldnt hurt to check my ground wires.
    #6
  7. Enkeiavalanche

    Enkeiavalanche Moderator

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    On a lot of new GM's you need to use a relay for the headlights if you hook up HID's.. Was this done?
    #7
  8. dobey

    dobey Member

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    You didn't mention in the OP what year the truck was or how long ago the HIDs were installed. You might want to check your ground wires (do the big 3 upgrade if you haven't), and also check your alternator and battery.
    #8
  9. The Heater

    The Heater New Member

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    The voltmeter on your dash tells you when there is an imbalance between the output of the alternator and that of the battery. First place to start is with the battery. Do you have a good battery charger (one that will run a float or maintenance charge of around a half amp when the battery is fully charged)? Simplest first step is to fully charge the battery. Lots of potential issues with batteries, but for this post, just saying to charge it. If you have a battery tester, great, test it. You can buy battery chargers that run tests on the battery and tell you its status. They cost more, but I have one and am glad I do. In any event, assuming your battery is good and it will hold a full charge, then see if a fully charged battery still causes the problem you describe.

    If you still get this information from the volt meter, I would have the alternator tested if you don't have a way to test it yourself. There are some voltage readings you can take with a simple volt-ohmmeter, off the battery with the engine running at certain speeds, don't have those values right here, or you can also buy a battery tester like one from Snap On (what I have) or another maker, and use that.

    The simple equation is that the voltage gauge is telling you the alternator is unable to keep the balance between it and the battery output. Could be something is wrong with the battery, the alternator, or you have some place that is taking power (or you have poor contact for the ground for the battery).
    #9
  10. redneckarmyMP

    redneckarmyMP New Member

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    Well I broke down and bought a yellow top Optima battery last week. Havent had any lights flicker since then and the voltmeter hasnt been bouncing back and forth whenever i push a button. Thanks for the input guys! If something changes I'll be back for more help!
    #10
  11. The Heater

    The Heater New Member

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    Make sure you save the instruction sheet for that battery. I have the Optima Yellow Top for my truck. If you drain the battery too low, you have to hook up a lead acid battery in parallel and then attach the charger to the lead acid battery until you get a certain voltage reading, after which you can hook the charger directly to the battery.
    #11
  12. PantheraUncia

    PantheraUncia New Member

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    I had flickering before I had my hid kit installed. I started going away when I put the new alternator in and upgraded to 2 yellow op batteries under the hood.

    I was also told that you could replace "The Big 3" meaning the main 3 battery cables in the truck by going with a heavier gauge wire than what the stock wires are.
    #12
  13. The Heater

    The Heater New Member

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    The only wire you need to think about altering is the wire going from your alternator to your battery. You could make it larger like 8 or 4 gauge, if you had put in a larger output alternator. Your other battery wires should work fine.

    And you don't need two batteries unless you are running off road and have a winch, or are running other external accessories like in a camper or travel trailer (but the latter would have its own batteries). The OEM battery in a deep cycle version should work fine for main stream accessories. I am running three amplifiers in my truck and I am not using a second battery or a power cell. No problems at all. And running a trailer with lots of lights and dual axle electric brakes was also not a tax on my battery or alternator, which is 170 amps (which is certainly not a super gonzo alternator).
    #13
  14. PantheraUncia

    PantheraUncia New Member

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    I thought the stock GM alternators were 105amp and 135amp, 170 seems like an upgrade? I was thinking about a 250amp, or dual 250 am alternators.... its not about what I have in the truck now, is about what i am adding on later. :)

    And while that second yellow top may not be needed for normal use, it did smooth things out with the electrical in my truck.
    #14
  15. SurrealOne

    SurrealOne Former Member

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    If memory serves the alternate/larger size is 145 amp?
    #15
  16. PantheraUncia

    PantheraUncia New Member

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    For my Truck:



    105amps is the standard and 135 is what they install as "heavy duty" on a 1500

    For you 2004 Sierra:



    105 is the standard and 145 is the heavy duty

    On a 2010 Silverado 1500:



    145 is the standard and 160 is the upgrade...

    I am seeing a pattern here....

    It would be nice if they just put 250 amp alternators in and called it a day, unless it need a dual upgrade or something like an ambulance, etc.
    #16
  17. The Heater

    The Heater New Member

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    My truck came with a 100 amp alternator. I had one built in the OEM case that has higher output, thus the 170 amp unit.

    My point is simply that you don't need to overthink your electrical. If you put in two AGM batteries, you now have double the charging load. If you don't have a need for it, why put it in if it is just going to be asking your alternator to recharge it?

    If you upgrade to a 250 amp alternator, one deep cycle battery can work for whatever you have going on, short of say a large winch or electrical from a camper or something similar.
    #17
  18. Need Mo Tools

    Need Mo Tools New Member

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    I had this issue on my 99 Tahoe. At first I also was looking at the grounds and battery cables. I have never been a fan of the side post terminals. I cut the red plastic boot off of the positive cables and separated the two positive cables discovering a lot of corrosion between them. I cleaned the cables and with a longer cable bolt from Advance Auto I put them back together with a crown washer between the two cables and between the cables and the side of the battery. I corrected my intermitent start issues but did not correct the headlight flickering. I traced the headlight to the alternator, bearing failing emitting red rust dust throughout the alternator causing arching. I suppose it was really messing with the the internal voltage regulator. I had been hearing the rumble of a bearing failure however I was thinking the belt tensioner was failing. I replaced tensioner and still heard the noise and then noticed the red rust dust coming out of the alternator. I replaced it and solved the problem. It has been fine ever since. I think a lot of starter motors have been replaced because of these side post cables and when you get corrosion between the cables the starter cannot get enough amperage to spin the starter.
    Good luck.
    #18
  19. The Heater

    The Heater New Member

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    Yellow Top Optima is what I am using.
    #19
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  20. Skippy

    Skippy New Member

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    Great information. Excellent post to keep others aware. I appreciate you following up with the solution!
    #20

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