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No low beams Ultra mount on 01 Silverado

Discussion in 'Western Plows Discussion' started by Brad Ent, Feb 15, 2010.

  1. Brad Ent

    Brad Ent Junior Member
    from CT
    Messages: 28

    Recently installed a used Ultramount on 01 Silverado
    (It was originally mounted on a Silverado)
    Four plug isolation unit
    High beams work but no low beams
    Bench tested headlights and both high and low work.
     
  2. twinman326

    twinman326 PlowSite.com Addict
    Messages: 1,683

    You made a statement about the mod..Is it a 4port/3wire, or a 4port/2wire??
    Have you tried changing the "plug configuration" for the head lights??

    What kind of headlights does the truck have??
     
    Last edited: Feb 15, 2010
  3. Brad Ent

    Brad Ent Junior Member
    from CT
    Messages: 28

    Four port isolation module, with four harnesses
    Truck headlights - four individual bulbs, from what I recall the connector plugs are two wire units.
     
  4. cubicinches

    cubicinches PlowSite.com Addict
    Messages: 1,412

    What year Silverado was it installed on previously?
     
  5. Philbilly2

    Philbilly2 2000 Club Member
    Messages: 2,633

    Got the same problem with an o6 and an o5. The fix I have been using is run the high beams. Hoping somone has the fix.
     
  6. twinman326

    twinman326 PlowSite.com Addict
    Messages: 1,683

    Then I am guessing you have a 4port/2wire..

    Like I said in post #2, you might have to re-configure the plug on port #1. On page 3 in the PDf, there are two "7.5 fuses". next to them (shown on pg # 3) is the "configuration plug". On page 6 it explain how to reconfigure the plug depending if your lights are "neg" ground, or "pos" ground (most likely your positive). Very simple and easy. See if that will straighten out your problem..

    If that doesn't work, put the configuration plug back the way it was, and check the harness once again to make sure everything is in its proper place.

    Here is the link to the PDF
    http://www.westernplows.com/pdfs/44780.04_052407.pdf
     
    Last edited: Feb 15, 2010
  7. Brad Ent

    Brad Ent Junior Member
    from CT
    Messages: 28

    Plow was on an 03 Silverado

    Yes, we tried to reconfigure with jumper wire and this did not work.
     
  8. cubicinches

    cubicinches PlowSite.com Addict
    Messages: 1,412

    Headlight plug in harnesses are different on '03 and up vs. '99-'02. If your wiring came from an '03, you should have 26351 and 26352. You need 26360-1 and 26361-1. Isolation module should be the same... 27781, light green label.
     
  9. x.system

    x.system Senior Member
    Messages: 368

    Simple fix without buying the other harness is to pull these two wires and flip them side to side in all 4 lights. I had the exact same problem as Brad is having. I uses a test light to release the prong on the long end of the plugs.

    [​IMG]
    [​IMG]
     
  10. twinman326

    twinman326 PlowSite.com Addict
    Messages: 1,683

    The reason for the switch, is because, GM change the "common" ground.

    I believe before 02, the common ground was "negative" .. 03 and on, the common ground became "positive"
     
  11. cubicinches

    cubicinches PlowSite.com Addict
    Messages: 1,412

    '99-'02 is positive common. '03 and up is negative common.
     
  12. Brad Ent

    Brad Ent Junior Member
    from CT
    Messages: 28

    I haven't had a chance to check the harness numbers yet.
    Will try flipping the plugs.
    Big snow on the way this week!
     
  13. twinman326

    twinman326 PlowSite.com Addict
    Messages: 1,683

    oops had the words switch around....All entitle to make mistakes
     
  14. Brad Ent

    Brad Ent Junior Member
    from CT
    Messages: 28

    Update:
    Swapped wires on hi and lo beams on truck both sides, still no lo beams on plow

    Headlight harness numbers are: 26351 Left side and 26352 Right side

    So any alternatives to swapping out the harness??
     
  15. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    You didn't re-pin them all. You have to do them at the 10 pin connectors at the Iso plug in end also. Need to reverse the blue and light blue wires in the 10 pin sockets J and K.
     
  16. JCI Trans

    JCI Trans Senior Member
    Messages: 313

    Ok i'm having the same problem, and found this thread on a search. My high beams work, but do i need to swap those connectors too or lust the low beams? Thanks!
     
  17. basher

    basher PlowSite Fanatic
    from 19707
    Messages: 8,992

    Follow the same instructions
     
  18. yamahadude9

    yamahadude9 Junior Member
    from none
    Messages: 1

    BIG THANKS to you and xsystems, i have a 99-02 harness and put it in a 03 truck and had hi beams only. Switched the 4 wires at the headlights and the four wire at the iso's j & k terminals and bam everything works !! Saved Me over $300 for the new wiring !!!!!! THANKS ussmileyflagussmileyflag
     
  19. 603chevy551

    603chevy551 Junior Member
    Messages: 11

    I'm having a similar issue with my fisher wiring harness on my 01 Chevy 2500. The harness came off of an 06 GMC 2500. It is a 4 port 3 plug mm2 setup. Am I correct that all I have to do to get the low beams to work is swap the wires left to right on all 4 lights and the swap wire j and k at port 3 & 4. All my lights work including high beam except low beams. I just to to make sure I won't short out my module.