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ultramount headlight problem

Discussion in 'Western Plows Discussion' started by delawnman, Jan 21, 2010.

  1. delawnman

    delawnman Junior Member
    Messages: 28

    okay guys, I've got an 07 gmc with a 4 port 3 plug module on it. We've never had a lick of trouble with it (its been on a couple of trucks and was new in 04). Suddenly yesterday the pass. headlight went dim. park and turn lights are all good. i bypassed the ground thinking that was it but no.The headlights on the truck are fine, We are not seeing any evidence that there is a break in the wiring so i plugged it into my other plow just to be sure it wasnt on the plow side and no it's definitely on the truck. I'm starting to think my isolation module might be bad but i cant swap out the one from my other truck as its a dodge. Soooo my question is this: is there any way to trouble shoot this without sending it to the local Western thief- oops i mean dealer- and i am open to any ideas you all may have thanx.
     
  2. twinman326

    twinman326 PlowSite.com Addict
    Messages: 1,683

    If you have a 4port/3wire mod ( with the same number; 26400/white label; 27781/green label; 26401/yellow label) on another truck (dodge) and the same number and color, I can not see why you can not use it to test your theory.

    That said, there is a test procedure, but you need a Isolation module tester. If you have one, here is the test procedure PDF
    http://www.westernplows.com/pdf/26473.03_110107.pdf

    If you have a 4mod/3 wire on another truck, I would try switching (as a test to see if it not the cable) the #4cables (pass side light). But if it off another truck that is not the same truck in question, I am not sure it will work, or if you had to switch the pins around for "plug configuration" depending what type of head light the trucks have.
     
    Last edited: Jan 21, 2010
  3. delawnman

    delawnman Junior Member
    Messages: 28

    no i dont have an iso module tester, and i hope not to do this often enough to need one, and gm used a different module from dodge (or at least a different part number)......
     
  4. twinman326

    twinman326 PlowSite.com Addict
    Messages: 1,683

    Yes one is a green label and the other one is a white label..That is why I was asking to check.. Sometimes they use the same.

    Also I mention about switching the #4 plug harness to see if there was a problem with the harness.
     
    Last edited: Jan 21, 2010
  5. delawnman

    delawnman Junior Member
    Messages: 28

    i can check more definitively in the morning and if i have to i can go to westerns site and see if the module numbers overlap. Have you had any experience with these modules going bad? if so, what symptoms did they give?
     
  6. twinman326

    twinman326 PlowSite.com Addict
    Messages: 1,683

    I just went to western and use the quick match..

    I use your 07 gm and a 04 dodge just for reference,

    using a 3port mod, they both take the same mod #'s. The light kit are the same, but the headlamp harness are different.

    If I knew what type of gmc, and what year and type of the dodge I have a feeling they would both take the same mod.
     
  7. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Pretty simple to test without an Iso tester, just have to know how to use a test light and what to check....

    Start with checking the black/white wire in port 2 for 12V with the plow connected and the low beams on. Should have it there. If you do then the Iso is fine and the issue lies between port 2 and the grill connector on that black/white wire.

    If you don't have 12V on the black/white at port 2 then you need to check the wire on pin A in port 4 for 12V (should be a yellow wire). Should have 12V there. If it doesn't then the problem is from there to the factory headlamp plug in. If you do have it there but not on the black/white you previously checked then the Iso is defective.

    But I think you'll find the issue lies in the wire harness's or a poor connection as the Iso's themselves seldom die.

    Be sure all grounds are good too...
     
  8. delawnman

    delawnman Junior Member
    Messages: 28

    now does each headlamp have its own pin coming out of the plug? because i have 12 volt high and low to one headlight but not the other.
     
  9. twinman326

    twinman326 PlowSite.com Addict
    Messages: 1,683

    Port 3 handles the left side vehicle, and port 4 handles the right side vehicle.

    According the the schematic;

    Port #3 (left side low/high out); D=red (high) E=Orange (low )

    Port #4 (right side low/high out); D=red (high) E=orange (low)

    Electrical diagram
    straight blade 4 port.jpg


    How far are you from Ithaca?

    straight blade 4 port.jpg
     
  10. delawnman

    delawnman Junior Member
    Messages: 28

    i'm about 15 miles from Ithataca, why do you ask?
     
  11. twinman326

    twinman326 PlowSite.com Addict
    Messages: 1,683

    How did you make out??

    Not too far from you
     
  12. delawnman

    delawnman Junior Member
    Messages: 28

    well i took the front clip off the truck and examined all the wiring going to and from the headlights to the isolation module to the plug connecting to the plow and found good connections and continuity throughout. The only thing left to do is to make certain that there is not 12 volts coming out of the isolation module - but at this point the only thing left is the isolation module itself. I actually live between mecklenburg and trumansburg.