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Another first problem of the year thread

Discussion in 'Truck & Equipment Repair' started by 82stang, Dec 15, 2009.

  1. 82stang

    82stang Junior Member
    from NY
    Messages: 19

    1993 Chevy S10 Blazer w/ Western 6'6" plow w/ Unimount

    Hooked it up for the first time this year, harness already hooked in and remains in last few years. No headlights on the plow unit. All lights on the vehicle work and the sidemarkers on the plow unit are lit. After examining the harness where the majority of all the splices are on the Driver side, I found a purple wire broke off a wire connector that goes in the harness over to the passenger side. The other side of the purple goes into the wiring for the vehicle lights I believe. It was easy enough to spot and the rest of the rats nest looked all intact. Right there is where there are two relays and about 10 wires going in and out. After reattaching the broken purple wire, still no headlights on the plow.

    My question is this. There are two relays right there, high and low beam. Could one or both be bad? How do I check them to see? What are some of your ideas on what to look for when everything works except the headlights on the plow unit. Bulbs are good.

    Thanks
     
  2. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    You want to check the brown wire at each relay for 12V when the truck lights are on as well as a good ground signal on the black/orange wires. If those two are good the relays should at least click when the trucks marker lights are turned on.

    And if the do click then the white on the one should have 12V when the high beams are on and the black should have 12V when the lows are on. These two wires head out to the plow lamps.

    For the full scematic see page 15 here.
     
  3. 82stang

    82stang Junior Member
    from NY
    Messages: 19

    I was looking last night and with everything hooked up...... the truck headlights are like this. High beams work, lows don't with plow connected. If I remove the plow and plug the vehicle plugs back into the lights, everything is normal and working. I remember also that I put a test light on the #80 terminal of each relay, as it said in the diagnostic papers I have from Western. It said there should be 12v from each spot when tested, test light hooked to pos battery terminal. Or do I need to be doing ground to neg terminal?

    Assuming the #80 terminals are the brown wires you are referring to, then when the test light was put on, I don't remember which, but one had a light, the other didn't. Does that mean the relay that didn't light when I did that is bad?

    Just for fyi, when i hooked the harness up 3 or so years ago, it was a rats nest that I thought I figured out. I got everything to work except a thing or two. I could get the marker lights to stay on, but not flash when I turned. And I only had one setting for lights on the plow, just high or low, when clicking the headlight switch inside the vehicle, the opposite setting for high/low made the plow headlights go off and no headlights on the vehicle. Sounds like a mess, but not really. It had lights and plow worked so that was good. Just never had flashers on the plow work and all bulbs are good.

    Thanks for your tips.
     
  4. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    The relays are wired wrong but lack of flashers on the plow has nothing to do with the relays, they're wired independently of them so you have more than one problem. It's the marker light connection into the truck wiring that must be functional as that's what trips the relays.

    Follow the diagram and trace the wiring and I think you'll find it needs some terminals moved and possibly a few connections repaired. You can verify all your work with a test light if you follow the schematics. To test for 12V with a test light you need the light connected to the NEGATIVE battery terminal. And to the POSITIVE if you're checking for ground.

    And look closely at the relay markings as there is no #80. It's 87, 87A, 30, 85 and 86 so be sure to positively identify each relay terminal while you're tracing or all your work will be futile. Numbering the terminals on each side of the relay with a paint marker makes it much easier to keep them identified.
     
  5. 82stang

    82stang Junior Member
    from NY
    Messages: 19

    My mistake on the #. It was 85 or 87, I just guessed when typing the post. It's clearly marked on the schematics. Thanks for the tips, I'll check when I can. It's been cold here.