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mvp plow lights won't switch

Discussion in 'Western Plows Discussion' started by pfd9544, Jan 24, 2015.

  1. pfd9544

    pfd9544 Junior Member
    Messages: 6

    when i plug my plow lights into truck harness, only passenger side head light and direction switches over to plow. drivers side stays on on truck.
  2. mishnick

    mishnick 2000 Club Member
    Messages: 2,353

    Assuming you have a uni-mount or a very early ultra with only two plugs at the grill you have a relay light control system. One of the relays is bad or there is a broken / corroded wire on one. There may be as many as six relays.
  3. nealybird

    nealybird Senior Member
    Messages: 750

    wait a minute. only the RH turn lights up on the plow lights? the park lights don't light up? If this is relay system, the relays get their power from the wire that's tapped into the park lights on the truck. so, are the park and turns all hooked up? was it working before, or did you just mount this wiring?
    btw, the park and turns don't transfer, they should be on on the truck and plow all the time.
  4. pfd9544

    pfd9544 Junior Member
    Messages: 6

    plow lights

    it is a MVP plus plow. everything worked a couple months ago when i pulled plow out of storage to get ready for winter. yes there are two wire harnesses in front of truck. there is isolation module with three plugs in it. i followed all plow wires under hood. could not find any relays.
  5. mishnick

    mishnick 2000 Club Member
    Messages: 2,353

    OK, MVP plus is a very late model multiplex plow, that's a whole different ball game, no relays on that one....

    When you plug in the 11 pin plug (at the grill) the isolation module should switch both headlights over to the plow, the plow marker lights should come on and the controller should light up. If one of the headlights doesn't switch over then you need to try a new isolation module. I don't believe wiring problems would do what you describe.