Dash lights "dimming" and other odd electrical issues

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by Bowtied, Feb 1, 2013.

  1. Bowtied

    Bowtied Epic Member 5+ Years 500 Posts

    2004 Silverado 5.4l 116,100mi

    Hey guys,

    Driving home last night I was assured of a problem I "thought" i'd been noticing. The dash lights (speedo, radio, electronics etc. prob even the headlights too) were dimming and then coming back to full bright, dimming and coming back to full bright.
    I thought i had noticed this before but thought i was just imagining things until i caught it happening twice in a row shortly after leaving work (engine was 1/2 temped up dunno if that makes a diff) then it went away altogether.

    If any of you have had a similar experience i'd like to outline some of the other weird electrical issues i've been having:

    -Some rain water got into the driver side window and seems to have affected the headlight twist-knob. The knob itself wont turn the lights on unless i press really hard "in" on the knob and switch it to the "on" position, (running lights come on, headlights dont) I have to leave the switch in auto and pray to god that the headlights do come on.

    -I tried to install an aftermarket radio once with the GM Door chime kit from Crtutchfield, i wired everything up removed the radio and the aftermarket simply would not power on, so i removed it and put stocker back in. everything was fine until after this last summer when i rode my motorcycle all season and the stock radio volume knob wont increase or, decreases while your trying to increase [very strange thing to describe, basically the knob is broke or some other electrical issue is compounded here]

    -The bulb on my oil pressure gauge went out 3 years ago or so, I dont think this is related but who knows.

    -The lights seldom come on when i open the door, just like the radio doesnt turn off after i take the keys out the engine power off and open the door (used to cut all electronics at this point) but now, the radio just keeps playing thank god this particular truck has an electronic cut off after ~15min all electronics cut off in case you leave your headlights or interior lights on (seriously).

    -When I roll the windows up there is an obvious strain on the electrical system as the dash dims, the headlights even strain until i release the window (even worse when Im trying to roll up both driver & passenger window at the same time)

    *I cannot stress enough whether the fact that leaving it sit all summer caused these problems to happen but most of these issues did not start happening until after the summer was over when i started driving my truck this very winter*

    Im really at a loss here, and I know its something very bad going on thats causing all this, is it possibly a short at the headlight switch? I've read that these go bad regardless, im sure mine is expounded by the fact that water from rain got in there. Could it also be rain on the window switch? I guess i need to get a voltmeter and start checking amperege, would a factory service manual tell me how much volts should be coming out of each electrical component?

  2. Curky

    Curky Epic Member 5+ Years 1000 Posts

    [MENTION=51590]Pikey[/MENTION] , calling you out because I think you have answered something like this before.
  3. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    As far as your interior lights not coming on and the radio not coming on, it is probably the door switch it is located in the door panel at the latch. They typically fail when the door starts sagging due to worn out pins. If you fix the pins you MAY be ok. I have a new battery and new alternator and my lights dim slightly when I roll up the windows also. This could be due to bad grounds. Especially the one from the cab to the frame. The bulb for the oil pressure is unrelated. As far as your lights dimming and going back to full bright. If your headlight switch is messed up , then there is a good chance that the dimmer switch in the headlight switch unit may be going bad. You could always track down a wiring diagram, pull the switch out and put a ohm meter on the correct pins (that control interior light dimming) You should be able to move the switch up and down and watch the resistance change. Alternatively, you could just replace the switch as you are already having issues with the headlights turning on, it might fix your issues, might not. But, you need a switch anyway and fixing your dimming lights would be a bonus.
  4. Bowtied

    Bowtied Epic Member 5+ Years 500 Posts

    Thank you these are great ideas in fact, i heard of people replacing the headlight switch with the AC Delco brand as it is more durable does this apply to my scenario? I Forgot to mention that my battery too, is brand new.

    Its really weird how the radio especially will go from hi to low as i try to increase the volume. when i tried to install that aftermarket radio, when i finally realized that it wasnt going to work i replaced everything as normal as possible and definitely did NOT cut into the harness or try any jerry-rigging of any sort, the only thing i can think of is that one of the connections back there might be loose as the radio sometimes gets SUPER hot as I drive 250+ miles from city to city on some of my business trips.
  5. j cat

    j cat Epic Member 5+ Years 1000 Posts

    with the miles on this I would check the alternator voltage output. these regulators get corroded the new alternators have the improved regulator.

    this is exactly how my alternator began failing. lights/dash volts gage would dim/drop.

    check all connections if there cleaned and secure then whats going on is the alternator output drops off and the you get only 12 volt battery power instead of 14.25 volts from alt.

    if its the alternator it will reveal this soon ..
  6. timcol

    timcol New Member

  7. darkness-lies-

    darkness-lies- Rockstar 100 Posts

    i have had dimming light issues also went and replace battery and alternator, Didnt help. check all my grounds they were fine. What i did to deal with the dimming was... i added two more grounds to the battery... now problem fixed. why? eh not sure seems like improper grounds. Also the multi function switch can cause the headlight issues. The switch that does you high beams , blinkers, and cruise.
  8. dirtbikerider16

    dirtbikerider16 New Member

    Can you explain a little further what your dimming issue was? I am experiencing something similar. While driving at night I set the dimmer to low, randomly it will go to full brightness for an inconsistent amount of time (anywhere from 1-60+ seconds). Changing the brightness with dimmer wheel has no effect. Just have to wait it out... Hopefully it's fixed by improving the grounding.

    I have an 06 GMC Duramax.
  9. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    I would pull the dimmer switch attach an ohm meter and check the resistance while moving the wheel. It should increase and decrease while moving the wheel. If not the dimmer is bad
  10. dirtbikerider16

    dirtbikerider16 New Member

    My dimmer wheel still works, I can adjust the brightness level. Just randomly the dash lights will go full brightness at night, and then the dimmer wheel has no control until they return to normal setting. Could this still mean a bad dimmer switch? I have not tested with an ohm meter, I will try to do that this weekend, but I suspect I will see the resistance increase/decrease as I move it.

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