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Blows 6amp Fuse

Discussion in 'Western Plows Discussion' started by fdmagic, Jan 23, 2014.

  1. fdmagic

    fdmagic Junior Member
    from NJ
    Messages: 3

    I have a ~2000 Unimount (Straight Blade) on a 2001 Jeep Wrangler (TJ). I bought it used and had a local equipment maintenance guy put the frame and wiring in. Since the old harness had been hacked out of the previous vehicle we had to go with a new one including relays, etc. The hand-held controller was used from the old installation. This is the version with Two Cables to the frame (Heavy Duty 2 conductor for the Motor Drive) and Multi-Conductor for the lights/solenoids. The cabling on the frame is original and looked Ok. After one (Very short) day of use the system starting blowing the 6amp SFE ignition fuse, I replaced and it worked for two or three moves then blew again. This happens while moving the plow and I am not sure if it is one or more directions that cause it but it seems to be L or R movement. I checked the coils on the solenoids (They should be 6.5 ohms according to Western) and they were Ok but I replaced all three just in case. The wiring in the coil box and around the frame looked Ok (No frays, cut wires, etc.). I took the controller down to the bench (It's 5 degrees outside and not fun to work outdoors) and using the wiring diagram from Western and their troubleshooting guide applied 12vdc to the controller and checked the function of all outputs (1,2,3) and the Motor Control (4) and they all worked correctly and timed out as they should. I am using a bench 12vdc supply so that I can also watch the current going out and the unit never ran over 150ma. So I concluded this unit is OK. I am about to go back out and spend I am sure a bunch of time running out the Brand New Harness to see if it got damaged in some way. I guess I should also mention that the motor solenoid is new but of course could have a coil issue. Any thoughts on something I missed or should check? After blowing out a box of fuses I figured I might take my bench supply out and hook it up to the ignition lead that way I can limit the current and don't need a fuse and then wiggle the wiring and look for the supply to go into overload and shutdown....other than that I hope I figure this out before the next big one!
     
  2. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    Look carefully at the wires under the valve cover. They often get pinched under the cover on the plow valve block.
    I have a little breaker from a highway truck that fits in the fuse socket. In parallel I connected a tiny 12 v lamp. When the breaker trips from a short the light comes on and no fuse blows. Good for the wire wiggle test. Check all along the controller cable from controller to motor relay all the way out to the grill plug for lights / controls. Probably a pinched or bared wire.
     
  3. fdmagic

    fdmagic Junior Member
    from NJ
    Messages: 3

    After spending an hour going over every inch of the wiring harness both in the vehicle and on the plow we could still not find any wiring issue. I decided to hook up an AC 12vdc supply to the ignition feed to the plow and set it to deliver no more than 5 amps to the system so that the power supply would kick out like a fuse at that point. After hooking up everything again, then removing everything one connector or wire at a time we isolated the issue to the 12vdc Motor Relay at the battery. When we removed the (+) wire going to the relay coil the problem stopped. Upon close inspection we found that the installer had dropped a star washer when connecting these wires down in between the relay body and the connection points, which intermittently shorted out the + and - coil connections. Simply pulled the washer out of its resting place and the system is not fully functional. Thanks for the pointers...
     
  4. fdmagic

    fdmagic Junior Member
    from NJ
    Messages: 3

    Sorry meant to say is NOW fully functional....
     
  5. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    Good to hear u found the problem. A star washer? Whodathunk!