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Millermatic 250 Surging Problem

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  • Millermatic 250 Surging Problem

    I have a MM250 that seems to be surging. It will not hold a continous arc at low voltage on thin metal. I have to turn voltage up to get it to weld and then its too hot and burns through. On thicker metal it sounds like it is surging and weak.

    i have a new gun and new roll of wire. Wire speed seems to be working fine.

    Any suggestions on where to start??????

    Last edited by JRS; 05-04-2013, 01:56 PM.

  • #2
    Hate to say it but the last machine that behaved like that (after checking all the obvious stuff) I know of was burned out. After you check all your connections and so forth for corrosion and looseness and try the diagnostic in your manual I would bring it in for service.


    • #3
      Unscrew the contact tip, makes sure is slides easily on the wire. Pull liner from gun, make sure it is not kinked, and that wire slides easily through it when straight. Also, make sure it is the right size for the wire you are using (size should be printed on plastic portion of liner). Make sure drive rolls are the right size. loosen tension screw and re-tighten according to the manual to make sure drive rolls are tight enough, do not over tighten. Make sure gun is inserted all the way, and that the tapered protio is close to the drive roll. Remove ground clamp, if it is the stock clamp throw it in the nearest trash can. Replace with solid brass/copper tweco, or the newer miller with the copper stud. make sure wire terminal is sanded to clean bright metal. remove terminals inside machine and wire brush until bright.
      This should solve most surging issues.


      • #4
        Thanks Walker, I will check those things.

        When I installed the new roll of wire it seemed to feed thru the gun fine and the wire speed control worked as it was supposed to.

        I do have the original ground clamp.

        After reading some other posts, I wonder if I have a problem with the circuit board.
        i have unplugged all the connectors and plugged them back in to no avail.

        I will post my findings.