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MM2 Light issue, need some thoughts, ideas

Discussion in 'Truck & Equipment Repair' started by AC2717, Dec 9, 2011.

  1. AC2717

    AC2717 Senior Member
    Messages: 669

    Hi Guys
    I have a 7.5 MM2 on a 2002 Dodge ram 1500 quad cab, with the standard light package.
    when I switch to highbeams (with the plow off the truck) My "Lamp out" light comes on the dash.
    When the plow is mounted and I try to go to high beams the plow lights actually go really really dim and also the Lamp Out light comes on in the dash.

    When I disconnect the plow light wiring hardnesses (putting the headlight back into the truch OEM wiring) from the truck head light and just run the head lights like there is no plow wiring in there at all, I do not have a problem at all

    Is it a relay in the wiring harness?? is it the control board for the plow wiring??? It is definatley something to do with the plow wiring, because I ruled out the truck OEM wiring by taking the plow wiring out of the equation and testing.
    Driving me nutzo:dizzy:
     
  2. 95HDRam

    95HDRam Senior Member
    Messages: 157

    Just my mechanic brain at work but sounds like a crossed wire in the harness or a short to ground with the lights dimming. I don't know anything about the Fisher plows so I can only speculate. Have you checked voltage at all your connection points to check for a drop?
     
  3. welder1122

    welder1122 Senior Member
    Messages: 114

    sounds like what ya got here is a failur to ground properly,

    trace all grounds associated with the plow wiring, the wiring for fishers needs to be ground just right or it wont work. if that fails than its the isolation moduale and from what ive scene/ heard they dont go bad often
     
  4. AC2717

    AC2717 Senior Member
    Messages: 669

    I will check the main gound this weekend. i was thinking it might be one of those relays in the line.

    I do not think there is another open ground on the unit am I correct in this?
     
  5. welder1122

    welder1122 Senior Member
    Messages: 114

    there should be a ground in the truck and a grond on the head unit
     
  6. AC2717

    AC2717 Senior Member
    Messages: 669

    alright so I claned up all grounds on the truck side, any and all touching the frame, body, and engine block. I connected the harnesses back to the bulbs. went to turn the high beams on (without the plow side on, but with all the plow truck side wiring hook in) and the same thing happened. Headlights dimmed and told me I had a bulb out.

    CHeck all the bulbs they were fine, also know this because when take off the bulb wiring and just put the headlights on without the plow side truck side wiring attached, high beams work just fine
     
  7. 95HDRam

    95HDRam Senior Member
    Messages: 157

    Voltage drop would tell you if 12+ Volts were getting to your Truck Side High Beams. But based on everything you have checked it sounds like somewhere in your Plow wiring is a short and is going to a ground source before it gets to the buld. The light on your dash will come on when the cicuit is not complete thinking that a buld is burnt out. It doesn't sound like a relay anywhere but a ground in the wrong location or a ground is not attached properly on your plow lights.
    Double check all your Pin Connectors on your Plow Wiring and see if everything is making a good connection.
     
  8. welder1122

    welder1122 Senior Member
    Messages: 114

    a good multimetter will test teh contunity of a wire. so u cna take all ur connections on the plow side and check to make sure everything is kosher. put the tester on the pin in the plug and the end of the line.