1. Welcome to PlowSite. Notice a fresh look and new features? It’s now easier to share photos and videos, find popular topics fast, and enjoy expanded user profiles. If you have any questions, click HELP at the top or bottom of any page, or send an email to help@plowsite.com. We welcome your feedback.

    Dismiss Notice

Problem with 2 plug MM1 harness

Discussion in 'Truck & Equipment Repair' started by CFM Services, Oct 3, 2014.

  1. CFM Services

    CFM Services Junior Member
    Messages: 9

    Truck: 99 F250 superduty 7.3 auto 4x4
    Plow: Late MM1 with instact pump - 2 plug, 9 Pin

    Just got the plow and harness. Harness was said to be off a similar year dodge, but who knows.

    I have a two plug mm1 9 pin harness. Has 4 relays, look to be plow high beam, plow low beam, truck high beam and truck low beam. I've got the plow functions itself (up, down, left, right float) working fine.

    Turns, and hazards work fine.

    Switches from plow lights to trucks lights as it should when plugging in or out.

    When you turn on just the parking lights, the head lights come on. There is no change when you switch to headlights from parking lights.

    There is no difference when you cycle between high and low beams. High beam signal is slightly illuminated on the dash when plow is plugged in. Seems to be back feeding.

    When plow is un plugged, driver headlight is normal, Passenger is very dim.

    My initial Reaction is that maybe something like the head light plug in is miswired from PO

    Any ideas on any of this?
    Last edited: Oct 3, 2014
  2. dieselss

    dieselss PlowSite Fanatic
    Messages: 11,392

    Not saying it's the smoking gun, but look into that pass light being dim.