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New Install, truck lights will not switch on

Discussion in 'Truck & Equipment Repair' started by hopkid929, Dec 27, 2012.

  1. hopkid929

    hopkid929 Junior Member
    from Durham
    Messages: 5

    Used fisher plow, new wiring, 2005 gmc 1/2 ton, MM2, three plug, insta-act, 3 port module with joystick.

    Thanks in advance to anyone who can help. I have been searching the forum but cannot find a similar issue. I have installed the new light harness kit, relay, power cable, control cable and adapter to the truck and have 100% function with the plow. My only issue is that I do not have truck headlights. If i disconnect the single power plug on the battery harness on the battery side, or single plug on harness A - module side, the headlights come back on (this disconnects power to the module, you can hear it switch off). It seems that the module cannot tell when the plow is disconnected, it is always trying to route power to the plow lights, regardless if the plow is connected or not.

    I have tried switching all the combinations of A side or B side on the HB3/4 plugs on the harness. I tried with and without daytime running light wire connected. I have swapped the module and a plow from another truck and still get the same problem.

    Any ideas? Thanks.
     
  2. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,988

    It seems that the module cannot tell when the plow is disconnected, it is always trying to route power to the plow lights, regardless if the plow is connected or not.

    thats odd,,,only thing that "tells" the module that the plow is hooked up is the bk/og wire off the plow motor, which getting gnd from the 2 plug
     
  3. unhcp

    unhcp PlowSite.com Addict
    Messages: 1,245

    could it be something with the Daytime Running Lights??
     
  4. hopkid929

    hopkid929 Junior Member
    from Durham
    Messages: 5

    So when you plug the motor into the power cable, it completes the loop and powers on the module?.. this would mean i have a closed loop on the power cable..seems to make sense. I'll check the cable tomorrow, seems pretty simple.

    Does the relay do anything more than route power to the pump motor?

    I don't think it has anything to do with the Daytime lights.. i tried both with and without.
     
    Last edited: Dec 28, 2012
  5. fordtruck661

    fordtruck661 Senior Member
    from CT
    Messages: 404

    Make sure that the 2 prong power/ground connecter is good they tend to burn out a lot. You may have to replace the plow side and truck side wires. You could take jumper cables and try to make a good ground with them.
     
  6. brad96z28

    brad96z28 PlowSite.com Addict
    Messages: 1,526

    Never hooked up a set yet.
     
  7. hopkid929

    hopkid929 Junior Member
    from Durham
    Messages: 5

    The truck power cable has continuity on each line, I have tried another plow that is working fine on another truck. I'm convinced it's on my wiring, but not sure where.

    This seems like a stupid issue, but I can see how disconnecting power under the hood every time is going to get old.
     
  8. unhcp

    unhcp PlowSite.com Addict
    Messages: 1,245

    Do we think it could be a bad module?
     
  9. CityGuy

    CityGuy PlowSite Fanatic
    Messages: 16,998

    I was thinking bad relay?
     
  10. hopkid929

    hopkid929 Junior Member
    from Durham
    Messages: 5

    It does sound like a relay problem, but I think it would be an internal relay in the module... the relay that connects to the battery and 2 prong power cable simply directs current to the hydraulic pump when actuated by the control ( I think)... so that would lead to a relay being stuck closed in the module... but I think I ruled that out also. When I switch to a friends plow and still had the same problem, we swapped modules after. It was off a dodge, but I still had the very same problem.. no truck lights with the plow disconnected.
     
  11. unhcp

    unhcp PlowSite.com Addict
    Messages: 1,245

    was the dodge module green 3 port?
     
  12. hopkid929

    hopkid929 Junior Member
    from Durham
    Messages: 5

    It was a three port, don't remember if it was green.. the plow worked fine though with that module.
     
  13. unhcp

    unhcp PlowSite.com Addict
    Messages: 1,245

    do you want to try another module? i have plenty
     
  14. CityGuy

    CityGuy PlowSite Fanatic
    Messages: 16,998

    I am not a fisher guy but in the westerns there were 2 relays. I would make sure both were hooked up correct accourding to the directions and if still nothing make sure head lights are plugged in. If still nothing then replace the relays. 20 or so bucks a piece.

    http://library.fisherplows.com/fisherplows/pdf/22372_050098.pdf
     
  15. unhcp

    unhcp PlowSite.com Addict
    Messages: 1,245