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Millermatic 200 Gas Feed Problem question

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  • Millermatic 200 Gas Feed Problem question

    Apologies for my first post be a "help me please post". I did search the archives and did not see a possible solution (not to say there isn't a solution there, but I was not able to find it!).

    I'm a very new owner of a MM200 (JD 675577 - Jan-July 1983) bought off Craigslist (the perfect way to move old non-functioning tools from a disillusioned person to an mechanically inclined optimist), which has the spot-welder card and controls, as well as the optional GA-40C gun and bayonet connector. The price was very low, so I'm not too surprised to see it has a problem .. I am not able to get the gas to feed to the gun.

    On the wire front: I have junked the rusty wire found in the unit and replaced with new 0.030" wire. Aligned the feed rollers, and removed, checked, cleaned and reinstalled the liner. Now getting good feed to the gun.

    Installed a newly filled CO2/Ar cylinder, but do not seem to be able to get anything through to the gun. Checked the cylinder by cracking the regulator coupling ... lots of gas escaping (2400lb/sq in). When I operate the gun, I get a solid click from the unit and the wire feeds correctly. I disconnected the gas feed to the GA-40 coupler near the wire feed mechanism and when I click th gun, I get a blast of gas, that then slows to almost nothing. It's seems as if I get gas feed for a very brief moment and then almost nothing. If I crank the regulator up to 65 cfh, I get a very low flow from the gas feed pipe.

    The unit will run a weld, and with the flow maxed out, it still look like sh*t, so I'm guessing that there is a problem with the gas flow to the gun.

    I have looked at the circuit diagram in the d/loaded manual from Miller, and I can see that the gas valve has a number of connections ... but wasn't sure how to start to trouble shoot the valve to get it to provide a steady feed of gas rather a momentary burst. Any thoughts?

    Many thanks for any advice offered. Now I a proud Miller owner, I hope to be be able to learn from other listers and in time, perhaps add my contributions!

  • #2
    Make sure the gun is pushed all the way in the feeder and the o rings are in good shape on that end. If you are getting gas at the rolls the problem is in the gun...Bob
    Bob Wright


    • #3
      Originally posted by aametalmaster View Post
      Make sure the gun is pushed all the way in the feeder and the o rings are in good shape on that end. If you are getting gas at the rolls the problem is in the gun...Bob
      Thanks Bob. I think I have eliminated the gun by disconnecting the gas feed tube from the gas solenoid where it joins the the GA-40 coupler (there is a small snap ring clamp that allows the gas feed tube to be disconnected at that point) so I can observer the gas feed from the tube when the gun is operated, before the gas gets to the gun. The following shows the tube disconnected. This is where I get an initial blast, followed by almost nothing ...

      Click image for larger version

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      • #4
        Thats a quick coupler, best now adays to eliminate that and stick a regular gun in its place. Have to reroute that gas hose back into the front of the drive.

        Anyhow, yes you'll get a burst of gas, now it dribbling off to nothing may mean that there is an obstruction in the line, or you have a CO2 only regulator.


        • #5
          Now fixed!

          Cruizer, good pointer. Swapped the regulator from my Lincoln and everything works fine. It looks like the CO2/Ar regulator that came with the unit is shot.
          Last edited by atgordon; 05-31-2011, 06:35 PM.