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Western unimount headlamps frying

Discussion in 'Western Plows Discussion' started by AJSequoia, Feb 9, 2015.

  1. AJSequoia

    AJSequoia Junior Member
    Messages: 4

    I have Western 7.5 Uni-mount which is just being hooked (again) after year of tranny problems/repairs on plow P/U vehicle. Everything assembled & looks good, however, upon connecting electricals and attempting to operate plow the headlamps started frying (i.e., smoking and burning up) along with headlamp
    harness wires. Plow seemed to receive power however would not lift or operate.

    I've checked (and re-checked) all wiring and connections (i.e., for rodent and other problems) and everything appears ok. Does anyone have direct experience or advice about this problem, or best way for isolating /diagnosing cause and cure? Much appreciated.
  2. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    First you need to figure out which electrical system you have. Uni had two versions of the basic wireing: 9 and 12 pin. All had one plug with two big pins to feed the pump motor but the 2nd plug is 9 or 12 small pins. In either case it will be relay controlled. If you haven't done any work on the plow (while fixing the transmission) and no rodents chewed you wires then it is probably a problem with the relays. There will be as many as six relays controlling the headlights. The markers and signals are connected in parallel with the truck so they shouldn't be the problem. Here is a link to the electrical schematics book: http://library.westernplows.com/westernplows/pdffiles/22373.07_110108_for_Web.pdf
    After you count the pins in your grill plug and count the number of relays just look for your system and start back tracking. If your wires were smoking then you should be able to identify what wire was overloaded and identify the color. Then look at the schematic and trace that wire back and systematically troubleshoot the problem. Not knowing what system it is or what wire is burnt I can't help you more than that.
  3. AJSequoia

    AJSequoia Junior Member
    Messages: 4

    Thanks for reply Mishnick - very useful. Will check system/2nd plug tomorrow for 9 or 12 pin, as well as, track relays and affected wires etc. Hopefully this will reveal source of problem and lead to repair remedies. I will let you know.
    Again, thank-you. Wishing you all very best.
  4. nealybird

    nealybird Senior Member
    Messages: 700

    holy crap. something must be hooked up very wrong. .... so the burning started right when you connected the grill connectors? or not until you tried a plow function? did the motor stick on until you disconnected it?
  5. AJSequoia

    AJSequoia Junior Member
    Messages: 4

    Gentlemen -

    Thanks for all responses and support.

    Mishnick - number of pins in 2nd plug = 9. Still working on tracing relays and wire, and will let you know.

    Nealybird - burning started as soon as attempting to operate/raise plow.
    It's likely plow motor remained on until I disconnected plugs, however, unable to say for sure as I got very busy reacting to a avoid total meltdown / fire. Suffice to say, some serious smoke /frying happened very quickly.

    Stay tuned... & Regards -
  6. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    I have a strong suspicion that your ground wire in the big two pin plug is not actually connecting to ground.... Looking at the 9 pin schematic the lights and the motor ground are common, that means if the motor is activated it will search for ANY ground and the alternative to the big wire is the black / org wire that goes through the 9 pin plug. Disconnect the 9 pin plug and then put an ohm meter between the motor ground and the truck battery negative terminal. There should be virtually no resistance. If there is more than one ohm examine the large negative wire from the battery negative post (or it could be on the engine block) all the way through the grill plug and on to the motor negative terminal. There will be some corrosion or breakage. That's what caused your smoking headlights....
  7. AJSequoia

    AJSequoia Junior Member
    Messages: 4

    Mishnick - you're the man - Thank-you!
    Will definitely track per your steps next 1-2 days. Wire corrosion and/or breakage is certainly possibility. As earlier noted, plow has been off vehicle for past 1 1/2 seasons due recurring tranny issues. 8200' elevation here w-some extreme season weather fluctuations.

    Thanks again & look forward report back soon. Cheers -