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  1. #1
    Bronze Member
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    Jinma 284, Kubota BX2660, IH Cub, Case 580CK, Minneapolis Moline 4 Star

    Default Did I ruin my new coil by reversing the polarity?

    I bought a 1959 Minneapolis Moline 4 Star for restoration because I liked its looks and was in really good condition. The engine did have a slight miss so I bought plugs, points, capacitor, rotor, cap, and wires. I put in the plugs first and no change. I put in the new points, capacitor, rotor, and cap next, tested it and saw only slight improvement. I next changed all the wires and found the problem -- the tower of the coil was completely corroded and the whole socket inside pulled out with the wire. I installed a new coil with the wire from the ignition switch to the positive terminal and the grounding wire from the points to the negative terminal. The engine just sputtered and could not run for more than 5 seconds. After a lot of cranking, I put the battery on a charger. I was really surprised to find that the tractor had a positive ground. The 4 Star was made for about 7 years and apparently all were positive ground. But my problem is: after correcting the polarity of the coil the tractor still won't start. Could reversing the polarity have damaged the coil or capacitor?

  2. #2
    Elite Member Industrial Toys's Avatar
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    Kubota R510 Wheel Loader + Cab and backhoe, JD 6200 Open Station, Cushman 6150, 4x4, ten foot 56 hp Kubota diesel hydraulic wing mower, Steiner 430 Diesel Max, Kawasaki Diesel Mule, JD 4x2 Electric Gator

    Default Re: Did I ruin my new coil by reversing the polarity?

    Unless there is some kind of electronic replacement, polarity should not be an issue, in my opinion. The capacitor is likely polarized and thus polarity sensitive. It would probably not work to capacity (in mfds) but I don't think it would be damaged. Such caps just clamp on don't they? So that would be the negative terminal. You would have to find a reverse one. Or attach a wire to the case and heat shrink it or similarly insulate it.

    Is the coil the right voltage? 6 or 12?

  3. #3
    Bronze Member
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    May 2013
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    Forest City, PA
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    Jinma 284, Kubota BX2660, IH Cub, Case 580CK, Minneapolis Moline 4 Star

    Default Re: Did I ruin my new coil by reversing the polarity?

    Thanks for the reply IT. The coil was 12v. I worked backwards putting back the original cap and rotor with no change. Put back the old coil and wire to cap with no change. Then put back the old points and capacitor and everything is fine. Point gap and everything was triple checked before going back to the old parts. The vendor for the parts has been contacted for refund or replacement.

  4. #4
    Elite Member Industrial Toys's Avatar
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    Ontario Canada
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    Kubota R510 Wheel Loader + Cab and backhoe, JD 6200 Open Station, Cushman 6150, 4x4, ten foot 56 hp Kubota diesel hydraulic wing mower, Steiner 430 Diesel Max, Kawasaki Diesel Mule, JD 4x2 Electric Gator

    Default Re: Did I ruin my new coil by reversing the polarity?

    AND, the Correct answer is . . . . . . ?

  5. #5
    Bronze Member
    Join Date
    May 2013
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    Location
    Forest City, PA
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    Jinma 284, Kubota BX2660, IH Cub, Case 580CK, Minneapolis Moline 4 Star

    Default Re: Did I ruin my new coil by reversing the polarity?

    It seems that the capacitor was damaged by reversing the coil polarity.

  6. #6
    Elite Member Industrial Toys's Avatar
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    Ontario Canada
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    Kubota R510 Wheel Loader + Cab and backhoe, JD 6200 Open Station, Cushman 6150, 4x4, ten foot 56 hp Kubota diesel hydraulic wing mower, Steiner 430 Diesel Max, Kawasaki Diesel Mule, JD 4x2 Electric Gator

    Default Re: Did I ruin my new coil by reversing the polarity?

    I find that a little hard to believe, but so be it. It's not a semiconductor. Do they make caps with the (outside) can being positive?

  7. #7
    Elite Member
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    Mar 2010
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    Ontario
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    CT235

    Default Re: Did I ruin my new coil by reversing the polarity?

    Compare the cam on the old vs new points. Or possibly the mounting location is different on the base plate. Your timing may have just been completely out to lunch.
    Tim.

  8. #8
    Bronze Member
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    May 2013
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    Location
    Forest City, PA
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    Jinma 284, Kubota BX2660, IH Cub, Case 580CK, Minneapolis Moline 4 Star

    Default Re: Did I ruin my new coil by reversing the polarity?

    Point well taken, no pun intended.

  9. #9
    Platinum Member ch1ch2's Avatar
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    DFW, TX
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    IH 584, NH TC33DA, NH TN95A

    Default Re: Did I ruin my new coil by reversing the polarity?

    Quote Originally Posted by nepa View Post
    It seems that the capacitor was damaged by reversing the coil polarity.
    I have bought brand new capacitors that were bad. Yours may have been bad new.
    Veteran US Army Infantry
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