Dimming Dash Lights

Discussion in 'General Chevy & GM Tech Questions' started by MeanGreenMachine, May 6, 2009.

  1. MeanGreenMachine

    MeanGreenMachine Rockstar

    I've got a mystery problem for everyone out there.
    My 04 Silverado LS 4.8 has a dimming problem. Every time I accelerate hard to pass, or have a little fun, my lights dim. All the lights! My interior dash lights, headlights, everything. I also notice some hesitation. This is the part that has me worried. I don't know if I'm going to hit the gas hard one day, and have my truck die. If I accelerate easy, I don't have the problem.
    I have an HO alternator, upgraded battery, and have upgraded the "big 3" wires to 2 gauge.
    I have also replaced the serpentine belt, belt tensioner, cleaned the remaining pulleys, to make sure there is no slippage there.
    I am running a single amp for subs, but I don't have to have the system on to see the problem. I also have a capacitor installed (FYI - If your lights dim with the beat of your bass, a cap will not fix it. At least it didn't in mine. The HO alternator did fix that problem)
    Does anyone have any other suggestions?
    My thoughts are that I still have another ground wire somewhere that is the culprit, but I don't know where to look.
    The local "Dealer" was able to see the problem and replicate the problem, but could not tell me how to fix the problem. They had it for 2 days!
  2. Jimmiee

    Jimmiee Epic Member 5+ Years 1000 Posts

    What I would do as a test is get a battery jumper cable and attach both cables to the negative battery post. Attach one of the other ends to the engine block and the other to the frame. See if the problem changes. If not try attaching one end to the body inner fender and one to the frame. You have a bad connection somewhere. Make sure someone didn't leave a ground wire disconnected from the transmission bellhousing. There's usually one going to one of the upper bell housing bolts.
  3. MeanGreenMachine

    MeanGreenMachine Rockstar

    I can't do the battery cable test. I guess I should have mentioned that it only happens when in drive, and usually right before shifting. So I have to be driving it.
    I will look at the transmission grounds. Strange though, I haven't had any work done on the tranny yet.
  4. Jimmiee

    Jimmiee Epic Member 5+ Years 1000 Posts

    You can hook up the jumper cables and close the hood. You could leave them on there forever if you wanted to. All this is doing is adding a supplemental ground to prove or disprove a bad ground circuit between your battery and engine / frame.
  5. MeanGreenMachine

    MeanGreenMachine Rockstar

    Could I attach an additional ground from the neg. battery terminal to the engine and/or frame?
    From what I understand, this won't hurt anything, as you can't have too many grounds. Or, have I been misinformed about this?
    I realize this doesn't fix the problem, but I'd rather have a cable bolted on as apposed to jumpers which could fall off.
    Thanks again.
  6. JMoney02

    JMoney02 Epic Member 5+ Years 500 Posts

    Did this come on all of the sudden? Or has it been working its way up to the problem? Did you notice anything prior to this? What or was anything modified before the ground issue.... Definitely sounds like a ground problem. Hows the capacitor ground, still tight? Jimmiee is right and yes you can bolt it down, but cable both the negatives together then a seperate lead to a ground source, but still see if all grounds are tight. What about the straps from the block to the body? And so on....

  7. daddytech

    daddytech Epic Member 5+ Years 500 Posts

    What everyone is missing here is 1. What type and size is your amp? and B. what are you pushing it with? you may just be pulling too much voltage for the truck to run properly and power all of your accessories and your stereo and amp at the same time.

    Example: I have a 1999 Tahoe with the police package options on it. 240 amp alternator, also have the second ac unit in mine and power everything but no 4wd.

    I have a Kenwood 898 Excellon stereo, one Crunch 1200 watt 4 channel amp for Mids, and one 2500 watt mono block amp for my 2- 12" Kenwood subs.

    I have installed a second battery in my truck with extra grounds galore (you can never have too many grounds and i have seen where they actually save gas on some counts too)

    I also have a 4 farahd Kole audio stiffening capacitor as well.
    now with all the facts here's what I experience: normal around town driving with the AC on and the stereo pounding the lights dim and the amp guage drops way down below 12 volts if i turn down the stereo or turn off the ac voltage goes back to normal but both along with the normal accessories that the truck uses are just too much for the factory 240 amp alternator even with the second battery. For the amount of power that my system is running the only thing I can do is add another battery or two which i am not prepared to do at this point or there is also an extreeme and expensive step i could take. A kit that you can buy that allows you to put two alternators on your vehicle also.

    I don't intend to put any thing more in or on my vehicle I just know that when i am running my ac I have to keep the sound down to normal levels or i could potentially have issues later on.
    I am running 4 guage wire for all my power wires from battery to amps the whole way through too so it's not the wire size that is the issue in mine either.

    here's a link to pictures of my system, you'll see that the amp i had in it when the pictures were taken was a 4000 watt Lanzar but that one burned up in 6 months so it's not the one in there any longer. it couldn't take the torture the way the Crunch amp I have now has. everything else is just as pictured still though, with the exception of everything being wire loomed now for protection and just because it all looks so much neater loomed up. oh yeah also not pictured is a 10 disk cd changer that is under the back seat on the passenger side as well.

    Last edited: May 7, 2009
  8. MeanGreenMachine

    MeanGreenMachine Rockstar

    It seemed to be all of a sudden. I never had any problems with it before that. The wiring/alternator/battery upgrades were all done for several months before I noticed it. The amp had been installed for a couple of years. And no work was done just before it started.

    Does anyone know of a diagram that shows all the ground straps on an 04 4.8? I have checked the ones I can see, but there may be more that I can't.
  9. MeanGreenMachine

    MeanGreenMachine Rockstar

    I can have all the accessories off - everything - and still have the problem.
    I can also crank my stereo all the way up and not have the pulsating lights (200 amp alternator fixed that). My amp is a 4 channel bridged to 2 channel, which pushes about 250w RMS to 2 subs.
    It is only under heavy acceleration that I see the problem.

    BTW - Nice setup on the system. You do the work?
  10. MeanGreenMachine

    MeanGreenMachine Rockstar

    Just wanted to update everyone on what I've found out:
    I checked all the grounds I could find, cleaned them off, replaced wiring where it looked like it needed to be done, etc. After all this, I still had the problem.
    I added another set of cables to the neg battery side, ground to chassis, then to frame, but neither way fixed it.
    On a hunch today, I switched back to my old alternator...and...it fixed the problem. Even though I had two different shops tell me the alternator was testing fine. Obviously I need to find a new place to take it when I need work done.
    So I am guessing the internal voltage regulator is not working on the HO alternator.
    The flip side is that I should never have to worry about grounds again.

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