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Western UniMount Light Problems

Discussion in 'Western Plows Discussion' started by big_daddy_sin, Oct 22, 2011.

  1. big_daddy_sin

    big_daddy_sin Junior Member
    Messages: 5

    Hello, I'm new to the site, but have used it many times to solve problems with my plow. I have a Western Unimount 7.5" straight blade that I recently removed from my 91 Silverado and installed in my 94 Yukon GT.

    The 94 Yukon is still the dual beam system that uses the 9005/9006 bulbs.

    The problem I'm having is that when I plug my harness in and turn on the lights, truck side lights do NOT turn off and the plow side lights turn on very very dim. Maybe half wattage. Additionally, truck side, the running lights are normal and the high beams are on also very very dim. Plow works perfect, no issues there. So when I plug in, all six lights are on.

    Last year I removed the wiring harness complete and installed it with out cutting any wires directly into my Yukon. Last week I checked the grounds, made sure it was metal on metal, replaced the three relays for the heck of it, checked any wire splices for corrosion, etc. All seems good. At the solenoid I recrimped the ground post leads and cleaned up the ground nuts, put dielectric grease on them. Also, last year I changed the plow side 12 pin connector as it was pretty scrody. I did not change the truck side unit and I'm not sure if it's really even a problem. When I plug the harness in, it seems like it wants to switch over but something is amiss.

    Initially I thought it could be a ground issue possibly restricting the relays from enabling. But when the truck is unplugged, they are fine. The only thing I have not done is change the head on the truck side or the bulbs plow side. I don't think bulbs would cause this problem.......

    It just occurred to me as well that I should check the bulbs plow side, even if it's not plausible that they could be a problem. The plow sat outside on the off season, and I have the old style unimount lights. Maybe it's possible the housing is filled with water, or there is corrosion in there.

    Any ideas? Any insight anyone can offer is greatly appreciated.

  2. big_daddy_sin

    big_daddy_sin Junior Member
    Messages: 5

    update - i checked the plow side bulbs - all seems good and dry, no bad wires or anything.
  3. mishnick

    mishnick 2000 Club Member
    Messages: 2,353

    You say you changed relays.... so I assume you still have the relay light switching system and have not upgraded to isolation module. On this plow the relays are only there for the headlights so it must be something to do with them or the related wiring. You need to down load the schematic and go through it step by step. The fact that the plow works indicates that the main relay ground is good because that is what activates the plow control. You say you moved the wires over without cutting any wires? When you installed into the new truck you should have cut and spliced into three truck wires. The left and right signals and the marker lights on one side or the other. You have to cut these wires, tap the plow harness in and then reconnect all three ends together in on joint. If you didn't do this then it shouldn't be working at all so I will assume that was just a mussunderstanding.

    Just to be clear, the old truck had four headlights and so does the new one right? And the plugs for the headlamp bulbs fit both the truck harness and the bulbs? Do the truck lights work correctly on both high and low beam when the plow is NOT connected? Do the marker lights and signals work correctly on the plow when connected?
  4. big_daddy_sin

    big_daddy_sin Junior Member
    Messages: 5

    Mishnick - thanks, yes I did have to cut and retap the marker/signal lights. I forgot to mention that, just meant I didn't modify the harness from one truck to the next.

    The old truck had the 4 bulb headlights and so does the new truck. The plugs for the headlight bulbs do fit both the truck harness and the bulbs, the fittings are all alike.

    Thanks for clarifying that the ground is good tho. I can stop sanding and re-crimping now.

    The highbeam/lowbeam lights work properly on the truck side when the plow is not connected. When it IS connected, the plow lights are dim, and the truck light's low beams remain on and the truck side high beams suddenly are on at the same time, dimly. (getting power somehow).

    Additionally, with the plow connected, when I flick on the high beams, the situation reverses: Plow side headlights stay the same, dim; however the highbeams light up and the lowbeam lights go dim. So it seems that when the plow is connected, truck side lights that should be off are somehow still getting transient power hence the dim bulbs. The fact that the plow side lights are always dim with no change when high/low is selected leads me to assume the dim truck side bulbs are somehow related. To me, the first thing I think is "relays". But I just changed those the other day.

    I could be wrong about that. It seems more and more that I have to go back to the schematic section by section, as you said. I suppose its possible that a wire is shorting somehow within the harness. Tomorrow I'll go through all the connections again. There are a few taped solders and small repairs that I'll strip back and take a look at as well.

    Thanks for the suggestion.
    Last edited: Oct 22, 2011
  5. mishnick

    mishnick 2000 Club Member
    Messages: 2,353

    Sounds to me like you are getting what I will call a ground feedback through your truck lights. I suspect that even though your old and new headlamps are the same style plugs they are not the same electrically. That is to say that the common pin is in a different place on the old than it is on the new. As I look in my electrical book I see that 1A/2A bulbs look the same as HB2, 2B/2D bulbs but the grounds are in a different location. If I were there I would try to reverse engineer the Western headlight harness and verify that all the wires are right. On most plugs you can pull the wires out and switch them. I am curious... do any of the bulbs have three pins or do all of them have two pins. If they all have two pins then I am wrong but if two of them have three pins then there is a chance I am right. The simplest way to fix your problem would be to order a new vehicle side headlamp / relay harness for the correct vehicle. If you can find someone who has the tables to look up the correct cable number for both the old vehicle and the new then you could compare them. If they are the same then you have something wrong with the right harness but if they are different then my feedback hypothesis is correct.
  6. big_daddy_sin

    big_daddy_sin Junior Member
    Messages: 5

    Mishnick - I checked the plugs and they are all 2-pin plugs, no 3 pin. Additionally, I tried unplugging the high and low beams at each connector to see if any plugs were causing a short. The plow lights did not change. It seems to have gotten worse. Now when I plug in the lights on the plow don't kick in at all. However the Truck side lights still both turn on at the same time, one regular, one dim. If I manipulate the truck side 12 pin plug back and forth, the lights go dim then off then come on dim again. My guess is it's a bad head. I'll try a new wiring harness/head and just shotgun solve the problem.

    Hopefully...... I considered just hotwiring the lights but decided against it.....
  7. mishnick

    mishnick 2000 Club Member
    Messages: 2,353

    You might consider eliminating the relays altogether and convert to an isolation module. They are so much simpler to install and troubleshoot. It's just a matter of money. They are compatible with both the uni and the ultra straight blades. Something to consider....
  8. big_daddy_sin

    big_daddy_sin Junior Member
    Messages: 5

    I was thinking that. To be honest, I had no clue they existed as I've only dealt with old plows, but when I learned about em I thought "so clean. so simple."

    I might start lookin around on local listings or ebay for a unit. meanwhile, the only thing I can do right now with the old harness is tear it out and seperate all the wires, look for faults. and replace the head. hopefully get that done today and post back.

    thanks for the suggestion