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headlight issues

Discussion in 'Western Plows Discussion' started by beanz27, Nov 17, 2014.

  1. beanz27

    beanz27 Senior Member
    Messages: 984

    I've got a Unimount MVP, just had new springs put on it. Get in and headlights and turn signals act as if plow isn't plugged in. No plow lights at all, truck side lights no problem. No issues with plow operating.

    Is this a relay issue? 97 F350 7.3 if it matters. Thanks for any help.
  2. mishnick

    mishnick 2000 Club Member
    Messages: 2,353

    The uni relays system completely isolates the light functions from the plow. There is a black wire with an orange tracer going from the relays to the 12 pin grill plug. This wire finds it's way to ground through the plow motor ground cable. Find this black / org wire on at the relays and jump it to ground. If the lights switch over to the plow then follow this wire to the plug and then on to the plow and finally to the ground lug of the motor. This wire is broken somewhere or the plug is bad. Beyond this we need more information to find the relay schematic for your truck. Can you count how many relays you have on the Western truck side control harness and what type of headlight bulbs do you have? HB5, HB1?
    One thing that all these relay systems seem to have in common is that they need power from the park lights on the truck to activate the relays. Find a brown wire that goes to pin 86 of any relay. If it's brown and on pin 86 it is a common wire coming from the park wire so it should have power at any point when the park lights are on. If not you can just put a jumper from battery + to the brown wire for testing. If that activates the plow lights then there is something wrong with the feed from the truck park light connection.

    One last question, do the park light and signal lights on the plow light up at all? Because these lights are connected in a simple parallel circuit with the truck. If the plow markers & signals don't work it gives us another clue either way.
    Last edited: Nov 17, 2014
  3. wahlturfcare

    wahlturfcare Senior Member
    Messages: 323

    I have a 93' that the lights wouldn't work and it turned out being a bad light switch plug as you had to wiggle the knob to get the headlights and marker lights to turn on at the same time.
  4. beanz27

    beanz27 Senior Member
    Messages: 984

    I'll have to take a look this weekend, haven't had time yet to look. Thanks for the very detailed post mishnick, I'll have to take a look.

    I tried wiggling the plug when I first noticed it, but it didn't do anything, so that's why I'm thinking relay. But maybe I just didn't wiggle enough lol. I'll keep you guys updated.