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99 high and low beams on at the same time

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by 53jimc, Jun 5, 2012.

  1. 53jimc

    53jimc New Member

    Hi Everyone,

    I have been searching for the past couple of hours, and doing google searches but am coming up with nothing for a '99 silverado. Does anyone have information on how to wire the headlights so the low beams stay on when you switch to high beams? I have hid kits installed on both, but, they take a few seconds to fire up. At 88fps that's around 300ft before you can see, scary.

    I'll keep searching but if you know of a mod, I'd appreciate if you could help.


  2. KyleZ71

    KyleZ71 Rockstar 4 Years 500 Posts ROTM Winner

    I know jc whittney use to sell some type of overide fuse i believe.. My father had it on his 96 tahoe. but then again he did not have hid lights
  3. SurrealOne

    SurrealOne Former Member ROTM Winner 1000 Posts

  4. ChevyHD

    ChevyHD Rockstar 100 Posts

    The diode won't work on his body style because he doesn't have two relays for high and low. You need to take the ground lead from you low beam and ground it to your truck.
    Last edited: Jun 5, 2012
  5. SurrealOne

    SurrealOne Former Member ROTM Winner 1000 Posts

    Thanks for the clarification. I wasnt' sure what he had in the fuse box. Was worth a shot...
  6. ChevyHD

    ChevyHD Rockstar 100 Posts

    Yup, I was hoping the diode would work as well for my truck but its rather simple to do it. Helps out a ton.
  7. 53jimc

    53jimc New Member

    Hi Everyone,

    I found this on another forum. The '99 only has one relay to control the high/low beams and I think it does it through the BCM.

    So, here are the instructions. I just did this and it works perfectly. Took 10 minutes, tops.

    and I quote:
    1) Open hood
    2) Remove brace from firewall to Driver's side fender.
    3) remove top of Circuit panel
    4) unhook the snaps from the passenger and drivers side of the cover...look hard they are there!
    5) Roll entire circuit board over towards the passenger side.
    6) Locate the Grey connector...there is only one.
    7) at location D3 (3rd down 4th to the right) is a light gauge yellow wire. It is the only yellow wire in this row.
    8) Tap this wire and ground it to the Light ground on the firewall. Follow the lead from the Hood mounted light, and you will find it ...just to the left (YOUR OTHER LEFT!!!) of the Master Cylinder.
    9) Put your stuff back are done...arent you glad you kept that cover?
    Enjoy your new quad headlights!

    I cut and pasted this from another forum but have done this and it works great. There is another way to do it using a relay but this is alot easier and since your working on the power side and not the dround you don't need a fuse. The lights themselves are fused on the power side of the circuit."
  8. ChevyHD

    ChevyHD Rockstar 100 Posts

    That's doing the same as what I said, just more complicated lol.
  9. 53jimc

    53jimc New Member

    LOL, yep. I guess it just spells it out... good thing is it works.
  10. ChevyHD

    ChevyHD Rockstar 100 Posts

    Yup, I'm glad you accomplished your goal!! lol its my favorite mod easily!

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