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No Plow Lights

Discussion in 'Western Plows Discussion' started by RathTR, Nov 24, 2012.

  1. RathTR

    RathTR Junior Member
    Messages: 16

    OK, I'm stumped. I wired the headlight harness in completely ('08 GMC Sierra Crew) and all I can get is the plow working but no lights on the plow whatsoever. The truck lights never go out. I went out and checked this morning after scouring this forum and found that I had the polarity reversed on the low beams. Stupid me, I thought "com" was negative and "low beam" was positive. That's what is stamped on the wires. Low and behold, 12 VDC was on the "COM" wire. Everything is connected right, "COM" is negative and both "HIGH" and "LOW" are 12VDC. Still can't get any lights on at the plow. Any ideas? I really appreciate all the help.

    Todd
     
  2. Sharpcut 1

    Sharpcut 1 Senior Member
    Messages: 386

    sdo you have running lights and turn signals? 08 chevy will have an extra wiring harness with 2 relays wired to it that plug into #1 port on module wiring harness to shut off high/low beam combo. iiiiif no running lights your tap isn't getting power and module needs input from wire.
     
  3. RathTR

    RathTR Junior Member
    Messages: 16

    It's as if the plow isn't even there at all. None of the lights on the plow come on and all of the truck lights work.
     
  4. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    So what kind of plow is this and how many plugs do you have at the grill? The way to go with this is to get the correct schematic and go over it connection by connection at the relays.
    The main thing we need to know to get your schematic is the number of plugs and pins at the grill. I expect you have two plugs, one with two big pins and the other with 12 pins. How many relays do you have too?
    The fact that the plow works indicates that some things are wired correctly. The plow is recognized by a loopback wire in the 12 pin plug.
    You were clever to recognize the common positive. That is one of the tricks with GM, some have common positvie while others have common negative.
     
    Last edited: Nov 25, 2012
  5. RathTR

    RathTR Junior Member
    Messages: 16

    OK, to quote Paul Harvey "here is the rrrrrrreeeest....of the story"...I bought this whole setup form a guy that had a 2005 Ford F150. It's a Western Ultramount Midweight Poly Plow. There are 3 connectors at the grill for connecting. I can't stress how good of shape this plow is in. It was used literally 5 times, and I got a smokin' deal on it. I took the whole setup over to a local Western dealer and showed him what I had and asked him what I needed to do to make it fit my '08 Sierra. He said I needed a GM light harness (which he swapped me even for the Ford harness I had) and a GM mount. I have the mount on the truck and now I am working on the wiring. The only relays I have are the 1 for the plow motor and the isolation module #29070-1. As far as GM using a positive common, I don't think that's the case here. But I could be wrong. I had the lights connected such that the "common" labelled wire was on the negative side and either "high" or "low" beam was on the positive side. I checked yesterday and found that I had 12 VDC on the "com" labelled wire. With the lights turned off there is no 12 VDC signal at all, which leads me to believe that the system is still negative common.
     
  6. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    OK now we get the whole picture..... 3 port Isolation module, awsome, that makes it sooo much simpler. And if a Western dealer gave you the headlight harness it should just plug in. You have four headlight right? Did you tie in the two signals and marker light wires yet? Those three wires are simply connected in parrallel. That means that the truck signals & markers will come on together with the plow signals & park lights. If your plow lights are not working you need to just unplug the Western harness plugs from the original vehicle harness headlight plugs and flip them over. When I do an install on the quad headlight GMs I look at the four orignal headlamp plugs and look for the color of the wires. There are two wires to each plug. All four plugs will have one common color. I look for that common wire and make sure the plug is flipped so that it matches up with the wire labelled as common on the Western headlight harness. That should be all you need to do. It can be a pain to get at the plugs especially if you have the battery on the left or two batteries. On the passangers side it's usually easy to get at by removing the air filter but on the driver's side the windshield washer bottle is also in the road. Depends on the year of the truck. Just plug in the plow lights, then turn the lights on and flip the wires one at a time until the corresponding plow headlight comes on. Do this with all four, two highs and two lows. Done !
     
  7. RathTR

    RathTR Junior Member
    Messages: 16

    I did that yesterday. I actually had the low beam connectors on the wrong way, and flipped them around yesterday. No change. All truck lights worked regardless of connector orientation and none of the plow lights have ever turned on.
     
  8. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    OK now it sounds like the isolation module is not switching at all. Does the controller light up at all? If not then first verify that all your ground interconnects are together. There are two of them, one at the adapter between the control harness and the headlight harness and another between the power relay ant the battery harness. They are little black, single wire connectors that have a black with orange tracer wire on both sides of both connectors. This wire completes a signal to ground to tell the controller and isolation module that the plow is there. First a signal is sent across from the truck side of the headlight plug, then it loops right back around and comes back to the truck where it must pass through the isolation module, then the ground interconnect at the adapter, on to the ground interconnect at the batter cable / relay and finally to the negative post of the battery. If any of those connections are open the plow will not activate and the lights will not switch from truck to plow.

    Follow this link and look at page three for the overview of the wiring system. http://library.westernplows.com/ddcommon/dd_pdf/pdfs/29206.09_050111.pdf
     
    Last edited: Nov 25, 2012
  9. RathTR

    RathTR Junior Member
    Messages: 16

    All of the single connectors are connected. That's the weird thing; I can get the plow to operate. The hand control lights up, and I can bump the "up" button and the motor runs and the plow jumps. I have not completely connected the plow yet. Just want to make sure all works first. So, hand control lights up, plow runs, but none of the lights on the plow turn on. BTW, I did splice in the signal and park wires as well.
     
  10. RathTR

    RathTR Junior Member
    Messages: 16

    Actually, in looking at the wiring diagram and my truck there appears to be three of those single connectors. All of which are connected.
     
  11. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    You are right about the three connectors, good eye! I forgot about the one at the isolation module plugs. But this new info is good, we know now that those ground interconnects are good and that the plow is being recognized. This narrows things down somewhat. Have you checked the two fuses at the isolation module? They are under a cover and have four wires going to them. I know they say park and turn but I recall some other issues with the headlights being associated with them. There are also two more fuses on the control harness near the adapter. But these two have no effect that I know of on the headlights. Still, won't hurt to check them. I wish I could see the schematic inside of the iso module to know how to test at the plugs, sucks that the schematic doesn't show that.

    Another thought.... is the red / org wire at the power relay connected to the "always positive" side of the relay? Use a test light, at the two fuses by the isolation module, if both these fuses light up then you know the fuses are good and the red /org wire is connected to the correct place. If not focus on that section of power feed.
     
  12. RathTR

    RathTR Junior Member
    Messages: 16

    Nick, thanks for all of your help and expertise. Unfortunately, I have run out of time and patience. I checked the wire at the power relay and it is indeed at 12VDC. I checked all of the fuses with a test light and they are all good, except for one of them that is at the isolation module. Only one of them has power to it, the other does not. At this point, I am going to make an appointment with the local Western dealer and let him wrestle with it. Probably will not be able to drop it off until Thursday so if you can think of anything else to check I will gladly do it.

    Thanks again,

    Todd
     
  13. RathTR

    RathTR Junior Member
    Messages: 16

    FOUND IT,FOUND IT,FOUND IT!!!!! I downloaded the 90 pagewiring diagram and got a chance to study it this morning. The two 10A fuses by the isolation module both get 12VDC from the same source. A splice embedded in the harness. I was only getting power on one of the two wires after the splice. Went out to the truck on my lunch break, pulled the harness apart, and guess what I found????? GREEN, and lots of it. The splice was soldered, shrink tubed, and inside the plastic protective wrapping and still managed to corrode. I attached a photo but it didn't turn out all that clear. Anyway, you get the idea. It's all fixed and all of my lights now work. WooHoo.....Thanks for everyone's help. It eventually led me in the right direction.
    Todd

    Corroded Splice.JPG