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9.5mvp power issue

Discussion in 'Western Plows Discussion' started by bartdude, Nov 15, 2014.

  1. bartdude

    bartdude Member
    from Chicago
    Messages: 45

    Need help figuring out a problem. I hooked up the plow to my truck and nothing happens.. I checked fuses and power to the cables and it seems to be fine.. I know the plow side is good because I attached to another truck.. Any thoughts? ISO module maybe?
  2. seville009

    seville009 Senior Member
    from CNY
    Messages: 877

    I had the same problem a month ago (8.5' mvp). Dealer replaced the headlight harness. Works fine now.
  3. mishnick

    mishnick 2000 Club Member
    Messages: 2,353

    Check the red ignition wire that comes off the control harness under the dash about a foot back from the controller plug. Make sure it has a good 12V connection to a switched power source.
    Do the headlights switch over from truck to plow when you plug it in or not? If not then check the ground interconnects. If this is a three plug setup then look for a black / org wire at the battery. It should go from the negative post to a black plastic single wire connector. Then look for the same wire, same kind of connector at the isolation module. If one of those is disconnected, corroded or broken you loose the ground on the plow presence detector curcuit and the truck will not know the plow is there. The lights won't switch and the controller will not light up either.
    If these options don't prove fruitful then get back to us and we will go to the next steps but give us the details, it's and MVP we know but what kind of light control system is it? Relays, 3 port isolation module, 4 port isolation module? How many plugs at the grill? If it's an old two plug (at the grill) with relays how many pins are in the plug with small pins, 9 or 12? One last thing, uni MVP or later model ultra MVP?
    Last edited: Nov 16, 2014
  4. Antlerart06

    Antlerart06 PlowSite Veteran
    Messages: 3,437

    I mine did same thing what mine end up being One of the plugs that under the air box didn't get truly snap together at install

    So my advice is check all plugs
  5. bartdude

    bartdude Member
    from Chicago
    Messages: 45

    Its MVP Ultramount with 3 port iso module. I checked with a light tester and it shows power to the plug.. I have been told by few people around light harness plug itself might be bad.
  6. mishnick

    mishnick 2000 Club Member
    Messages: 2,353

    "I checked with a light tester and it shows power to the plug." What plug? If you found power at the black controller plug that means nothing as far as the ignition power goes.

    Go to the isolation module, pull port C and check pin C. This is where the ignition wire goes. It should be hot with ignition only.

    If that is OK check port C pin F and port B pin F, both of these should be hot all the time. If not look for two fuses near the isolation module, they are both under one cover that looks like a plug with four wires. If they are not both hot then go to the motor relay and recheck the two fuses there. One is 7.5 A (this one does nothing ) but the 15 A feeds the previous two fuses and the two F pins at the isolation module.

    If this is all good then we need to look at the plow presence ground circuit.