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Fisher mm2 multiple light trouble

Discussion in 'Fisher Engineering Discussion' started by TMLGC, Oct 28, 2014.

  1. TMLGC

    TMLGC Senior Member
    Messages: 207

    Only drivers side low beam works and both drivers and passenger high beams. No parking or turn signals at all. All truck lighting works as it should. Background below.

    I got a 8' Fisher mm2 (3 plug) used from my neighbor. I brought my 2005 2500HD to Fisher dealer, Weirs, and had them put all truck side parts and wiring on. They were able to keep/use the controller and the 3pin harness wire that connects and goes to the pump. Everything else was new truck side. Including new 3 port ISO and new 11pin harness truck side out to plow.

    On the plowside there were after market lights spliced into the 11pin plow side harness that looked like it had been repaired in the past. I figured just replace both with new Fisher prewired into a new 11pin plow side and be done with it. I was suprised to see same problem????? These are now new lights and new truck and plow harness going together. I found 4 fuses related to the plow and checked connections to make sure things were plugged in.

    My thoughts are this is a truck side problem now?

    Any suggestions if it's something simple to check before heading back to dealer?

    Plow itself works fine up and down side to side.
  2. NHresident

    NHresident Senior Member
    Messages: 285

    have u chked the bulbs themselves IF u hve the older style plow lights the parking bulbs and directionals get real bad with rust
  3. TMLGC

    TMLGC Senior Member
    Messages: 207

    The complete light set up is brand new last night. New fisher lights and already wired into a new 11 pin harness. I switched the A B plugs at the truck head lights and just opposite problem. Both low beams then work but only one high beam and still no parking or turn signals at all.
  4. TMLGC

    TMLGC Senior Member
    Messages: 207

    Also prior to replacing the light set up it was exact same problem. I figured if truck side was new and now plow side was all new it would fix it, not so. That's why I'm guessing truck side somewhere.
  5. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,743

    Have you looked on fishers website at the wiring diagrams?
  6. TMLGC

    TMLGC Senior Member
    Messages: 207

    Okay after searching searching some more it seems that the most common issue is the AB plugs at the headlight. I switched them around on the passenger side and that fixed the headlight issue.

    So both headlights hi and low work as they should now.

    Still no parking or turn signals in the plow at all. Those seem to be hard wired in???? Any ideas on those
  7. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,743

    Yes. You gotta start at the trk side, where they spliced into your factory wires. Then follow that into your Iso module, then back out to the plow
  8. Its an '05 so just pop the headlamp assemblies out and look at the turn signal assemblies below and see if they spliced the fisher harness in there.
  9. TMLGC

    TMLGC Senior Member
    Messages: 207

    Okay quick call to Weirs straightened me out. I had the black orange grounded to just the frame. I did not realize the parking/turn lights are powered seperate from headlights. They said remove the bolt and ground it to stud on motor where the other black wires are. Did that and everything now works as it should! :)

    I can see how those AB wires can get flipped around there is no orientation that I could tell. They originally had put 1 of the 4 on backwards which caused the headlight issue. The parking light issue was on me
  10. chevyzrule810

    chevyzrule810 PlowSite.com Addict
    Messages: 1,214

    Glad to see you got it fixed