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Head lights switch back and forth for no reason.

Discussion in 'Truck & Equipment Repair' started by jimbo15, Dec 23, 2009.

  1. jimbo15

    jimbo15 Junior Member
    Messages: 2

    My western plow headlights work fine for a little while then go off and my truck lights come on. What is going on? Should I replace the relays on the harness? Help
  2. festerw

    festerw Senior Member
    Messages: 986

    Do your lights automatically switch when you connect the plow? If so I'd clean the connectors very well and coat them with FF or dielectric grease.
  3. sparky2410

    sparky2410 Member
    Messages: 43

    I agree with festerw
  4. jimbo15

    jimbo15 Junior Member
    Messages: 2

    Sometimes they do and sometimes they don't. I will do a clean on the connectors. Thanks
  5. elite1msmith

    elite1msmith 2000 Club Member
    from chicago
    Messages: 2,762

    i assume this is a really and not an issolation mod.

    i dont have the wiring diagram in front of me, but i got a few things for you to look at.

    when the plow lights turn off, do you loose anything else? due the parking lights stay on with the plow? does the plow fuction properly? DUE THE BRIGHTS ALSO FLIP BACK THE FORTH

    Id start with cleaning your connections. both on the plugs, and also on the relays.

    heres how the system works, and if there is a problem this could possibly be it. The head lights, and brights use two seperate relays, so IF you have a problem with only the headlight and not the bright, id suspect the relay.

    If they both dont work properly, heres what happens - Power flows thru your trucks wiring harness, is spliced into the relays. if the relay is off, the power goes back to yoru trucks head lights, if the relay is on, then it goes to the plow. Beacuse your getting the lights to work at both plow and truck..this is not your issue

    in order for the relay to turn on, it must recieve a pos+ signal from the Parking lights. and it must receive a ground return signal from the plow. So, normally speaking, if the parking lights were good on the plow, then odds are the connection is also good for those relays.

    the ground return. - power flows thru the neg cable , thru the plug to the motor on the large plug on your plow. a smaller black and orange wire the takes that power, diverts it to the solinoids, head lights on the plow, and then BACK TO THE TRUCK thru the other 9 pin plug. This ground return is how the relays know your pluw is plugged in. It also turns on your controller. If you notice with the plow unpluged the controller will not turn on, Unless it has been grounded speratly, (which i have seen)

    so if its the ground return , odds are the controller would turn off, however its best to acctually test each part of this circit with a light tester and verify what the problem is. Its hard to test things that dont always happen so, you can try jumping power and ground (one at a time) and see what the problem is