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  1. #1
    Platinum Member marrt's Avatar
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    Northern VA
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    Power Trac 1845

    Default Three post starter relay question

    My tractor has a three post starter relay like the one in the picture below. The small post in the middle goes to the starter solinoid. I ordered a new one and they sent me a four post relay. One small post going to the starter solonoid and one going to the ignition. Can I still use this relay even if I don't connect anything to the ignition? Or does the ignition circuit have to be energized for the relay to work?

    Three post relay...


  2. #2
    Veteran Member kevinj's Avatar
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    Jul 2003
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    1,314
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    West MI
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    BX-1860, L3940HSTC, B7500, Farmall M, Farmall 560D

    Default Re: Three post starter relay question

    You will need to check your wiring with a meter. The 3 post is internally grounded and the 4 post probably needs a ground wire for the coil.

  3. #3
    Platinum Member
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    Apr 2005
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    Erin, Tenn.
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    2001 Mahindra 4110

    Default Re: Three post starter relay question

    The three post relay you show is for later, electronic ignition systems and/or a diesel engine. The small post should be connected to your start switch - keyswitch or button switch, and 1 large post goes to your battery and the other large post to the starter. The relays with the extra "ign" terminal are for older, point- type ignition systems. A point system ignition coil does not operate at battery voltage normally, they have a ballast resistor(internal or external) to drop voltage normally to about 9 - 10 volts (12 volt systems). For starting only, there is usually a wire from the "ign" terminal on the relay to the positive coil terminal - when the relay is in the energized, start mode only, it delivers full battery voltage to the coil for better spark for starting. When you release your starter switch, this "ign" terminal is off and the coil is operating on resisted voltage again thru the ballast resistor. I guess in rare applications, this terminal could be used to supply battery voltage to something else, but it will only be live while in the start mode. The case on the relay is the ground for the solenoid inside - make sure it has good, clean contact with grounded metal.

  4. #4
    Platinum Member marrt's Avatar
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    Mar 2002
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    535
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    Northern VA
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    Power Trac 1845

    Default Re: Three post starter relay question

    Thanks for the response. I have a diesel engine and originally used the 3 post relay. If I read your post correctly, I can just hook this up as before and "ignore" the fourth ignition post. Correct?

  5. #5
    New Member
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    Mar 2005
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    Location
    southern indiana
    Tractor
    kioti dk45

    Default Re: Three post starter relay question

    Correct just ignore the 4 post

  6. #6
    Platinum Member
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    Apr 2005
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    715
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    Erin, Tenn.
    Tractor
    2001 Mahindra 4110

    Default Re: Three post starter relay question

    Yes, just ignore the "ign" terminal but make sure the relay is rated to handle your starter draw - most I have seen are, but a larger diesel engine and/or a worn starter could cause excessive draw on a lesser-rated or really cheap quality relay.

  7. #7
    Epic Contributor Soundguy's Avatar
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    Central florida
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    ym1700, NH7610S, Ford 8N, 2N, NAA, 660, 850 x2, 541, 950, 941D, 951, 2000, 3000, 4000, 4600, 5000, 740, IH 'C' 'H', CUB, John Deere 'B', allis 'G', case VAC

    Default Re: Three post starter relay question

    Guess he could parallel them if it was exceeded.

    Soundguy

  8. #8
    Platinum Member marrt's Avatar
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    Northern VA
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    Power Trac 1845

    Default Re: Three post starter relay question

    Thanks guys. I'll give it a shot in the next day or so. It is a cheap Made in China relay. Paid $6 at Surplus Center...so I bought two. The picture I posted was of the one I was supposed to receive. Anyone know a Made in USA source for these?

  9. #9
    Platinum Member
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    Nov 2002
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    Location
    Strasburg, OH

    Default Re: Three post starter relay question

    NAPA auto parts or your local equivalent.........nearly every ford built in the 70's thru the mid '80's used that type of starter relay.

  10. #10

    Join Date
    Aug 2002
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    7,386
    Location
    North East CT
    Tractor
    2003 Kubota BX-22

    Default Re: Three post starter relay question

    Cole Hersee makes some of the best relays that you can buy. They are also some of the most expensive on the market. Unfortunately so many parts today are made in China, that it is difficult to know if the part that you purchase is a quality one or not.

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