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Fisher MM2 no up, down, left, right

Discussion in 'Truck & Equipment Repair' started by barret, Feb 14, 2014.

  1. barret

    barret Junior Member
    Messages: 3

    I just wanted to share this in case it might help someone in the future.
    Out of the blue just when I needed it the plow decided to stop working. A quick check of the power light on the controller showed OK.
    Summary of symptoms:
    1 No plow operation
    2 Power light good on controller
    3 Solenoid clicks once then stays engaged even with power switch turned off on the controller and the ignition switch off (solenoid gets warm)
    4 With the solenoid stuck engaged the power light will light when moving the joystick with the ignition off and the power button off on the controller. (odd)
    5 Solenoid will disengage by unplugging the three pin harness and then its Ok to plug it back together.

    All fuses checked (good)
    Using a volt meter checked for power out of solenoid (good)
    Checked power and grounds at two pin harness (good)
    Jumped motor direct with battery cables (working good)
    Cleaned all harness pins male / female, checked for good tight connections
    Cleaned all main large battery cable connections power and ground sides at solenoid, motor, and battery.
    Wiggle tested all harness's
    No luck to this point.

    The light coming on on the controller with the ignition off when I moved the joystick kept telling me a bad ground. Noticing the plow hydraulic flow control solenoids received a common ground from the main battery ground connection at the bottom post of the plow motor I decided to check this further. Back to the two pin harness. This time a good wiggle test and a tug at the back side of the harness revealed the problem. The ground was not connected internally to the bullet connector. Swapped out the harness and good to go.

    The bad ground at the harness didn't show up with the meter more than likely due to a no load condition using a meter.


    Last edited: Feb 14, 2014
  2. LON

    LON Senior Member
    Messages: 749

    Had a customer that had his ground wire rot right in the middle of the harness. Took quite a while to find it as well. No marks in the covering, no bulging of the insulation. Little puff of smoke was what finally made us see it.
  3. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,739

    That's why its always better to use a test light. Meters lie
  4. barret

    barret Junior Member
    Messages: 3

    I suspect a test light might have shown a problem but in this case a low amperage draw test light would have more than likely lit ok. A better test in this case would have been something pulling more of a load like a old style headlamp or an old blower motor.
  5. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,739

    Any load would have shown something. A meter dosent load test