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Thread: Sa-250 wiring issues

  1. #1
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    Sa-250 wiring issues

    I recently got a new to me mid '80's Lincoln SA-250 and i am in the middle re-wiring the whole thing. It seems that I have got everything wired up correctly, except for the two wires that come off the oil pressure sensor. This machine has the manual pull shut off knob, so no electronic ignition or anything that I could see the oil pressure sensor shutting down.

    Can some of you guys look on your machine and see where those two wires go. And pretty sure one of the wires goes to the back of the amp meter and the other I don't know.

    There is also another unit on the machine pictured below that I have no idea what it is and what it does. Do any of you have any ideas what it's for?

    Thank you in advance!

  2. #2
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    Re: Sa-250 wiring issues

    Lincoln SA 250 code 8568 Name:  PXL_20220425_015927224.MP.jpg
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  3. #3
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    Re: Sa-250 wiring issues

    That is ignition ballast resistor. Ok, as I recall the oil pressure switch was in series with the coil wire from ign. The ballast resistor just before the coil, one wire from a start terminal on ign switchgoes to coil and the ign/run wire goes thru the resistor. They could have T the start wire with 1 terminal on the ballast too and share the wire to the coil. The idea here, engine not running and making oil pressure no start. The resistor is placed so its bypassed at start and then feeds the coil which reduces voltage thru the points during run. Gives it a little boost at start then reduces to extend point life.
    Last edited by Sberry; 05-06-2022 at 11:02 AM.

  4. #4
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    Re: Sa-250 wiring issues

    Quote Originally Posted by Sberry View Post
    That is ignition ballast resistor. Ok, as I recall the oil pressure switch was in series with the coil wire from ign. The ballast resistor just before the coil, one wire from a start terminal on ign switchgoes to coil and the ign/run wire goes thru the resistor. They could have T the start wire with 1 terminal on the ballast too and share the wire to the coil. The idea here, engine not running and making oil pressure no start. The resistor is placed so its bypassed at start and then feeds the coil which reduces voltage thru the points during run. Gives it a little boost at start then reduces to extend point life.
    This unit pictures his wired into the welding side of the generator. One of the two smaller wires coming out of the main generator goes into the right side of that, and then coming out the left side goes to the outside of the rheostat. I don't see this unit on any of the wiring diagrams I have ever seen from Lincoln. I bypassed it and it seemed to weld a little hotter without this unit. So I'm not sure if I need it or not. It seems to still be working correctly.

    As for the oil pressure switch wires, this is a Perkins diesel unit, and there is no ignition at all. There is just a start button and an a shut down knob that you pull.

  5. #5
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    Re: Sa-250 wiring issues

    Whoops,,,,,,, totally went by me it's diesel. Is there electric fuel solenoid on inj pump?

  6. #6
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    Re: Sa-250 wiring issues

    No fuel solenoid on this unit. Its all pretty basic with no bells and whistles. That's why it's got me scratching my head as to what the pressure gauge does.

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