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New headlamp harness not working

Discussion in 'Western Plows Discussion' started by DJC, Nov 12, 2011.

  1. DJC

    DJC Senior Member
    Messages: 481

    Hello,
    I wired up a new plug in 6 relay headlight harness on a 01 GM and I can't get the lights on the truck to work correct. I am 100% sure all the wires are hooked up right on the relays but I tried it twice and as soon as you turn on the lights it will blow the left side headlamp fuse in the truck. that leaves the passenger low beam and high beam on at the same time and the low beam on the drivers side is very dim. I think I'm at a dead end now because I have no idea what to check. Any info would be greatly appreciatedThumbs Up

    Forgot to mention it's a 12 pin harness for a MVP
     
  2. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    If your truck lights worked before you put in the plow harness and now it doesn't there is only one logical conclusion. Something on the relay harness is not right. It is possible that the harness is wired wrong from the factory, but no likely. It it were my project I would be testing the harness to be sure the wires go where the schematic says they should and that it has not been modified by a previous owner if it is used. Then I would start from scratch and reconnect the wires to the relays. But don't just hook them up, figure out what the purpose of each connection is for, make sure it makes sense. Understanding the curcuit is the key to troubleshooting. You need to understand how the system works in order to come up with logical tests to verify proper operation.
     
  3. DJC

    DJC Senior Member
    Messages: 481

    Funny thing is the harness I went and bought from a western dealer only come with 4 relays and all the diagrams I have is showing 6 relays. They tell me 9 pin and 12 pin makes no difference and the this headlamp harness 63394 will work with a strait or MVP.
     
  4. DJC

    DJC Senior Member
    Messages: 481

    This may sound like a stupid question but I'm not a GMC person. To "tap" into the DRL's it's the little lights on the inside, next to the grill correct??
     
  5. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    If they say it will work I would assume it will but it would have been nice of them to sell you what you wanted and understand. I am not terribly familiar with the old relay systems. When I see them they are usually so messed up we rip them out and upgrade to isolation module so I rarely get to troubleshoot them; however, I do have the electrical manual for the MVP from Western school and there is a section that shows a six relay schematic on page 86. I took the literature number and found a link at the Western site, here it is... http://library.westernplows.com/ddcommon/dd_pdf/pdfs/22373.07_110108_for_web.pdf In the third section tittled "Relay Systems" you will find every curcuit ever put out by Western. Without being there to look at your truck this is the best I can do. Hope it helps.

    I have to go to work now so I will be off line until tomorrow, good luck.