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Millermatic 200 Gas Valve

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  • Millermatic 200 Gas Valve

    I have a Millermatic 200 I bought new in 1991. Serial number is KB101648. A few weeks ago, when I first started to weld, it took a couple of pulls of the trigger to get the gas to flow. I didn't think anything of it at the time. When I went to use it the next time (yesterday), it would never activate the gas flow. Wire feed, etc., works fine, but no gas. I doubt it's the flow meter, as the steel ball floats up when you first open the cylinder valve.

    The manual say the gas valve part number is 116-996. It can't find that part number anywhere, even on Miller's site. So, what do I do now? I don't want to give up on it, as it's in mint condition, and I've never had any other problem in 30 years.

    Thanks,
    John

  • #2
    First thing to check is whether it's the gas valve, or the relay that actuates it. Do you have a multimeter and are you comfortable with checking live voltages? Or can you get someone familiar with electrical things to help? If so, set your multimeter on AC volts, on a range that will measure 120 VAC if it does not have autoranging, and connect one lead to each terminal of the gas valve. DO NOT hold a meter lead in each hand--user alligator clips for at least one terminal. Never allow the possibility that current could flow arm to arm through your heart in the event something goes wrong. Remember you are dealing with live 120 volts. In this circuit, one lead of the valve is always "hot" when the machine is on, connected directly to the transformer, so use caution, and the other is connected to the other side of the transformer by the relay contacts to energize the coil and open the valve.

    Pull the trigger on the gun, and you should read around 115 VAC on the meter. If you do, it is likely the gas valve; if not, relay CR1 is bad.

    Any gas valve from any welder that uses a 115-120 volt AC coil will work. You have have to jury rig a mounting bracket of some sort, but as long as the coil voltage is correct and the plumbing fittings match (or can be matched with some adapter fittings from the hardware store), it will work. If you call Miller, they will probably be able to give you a new part number that will fit, but it may be pretty pricey if you buy it from them. On the other hand, it should just fit with no messing around. If you need the relay, same thing--should be able to find a generic relay with little effort, and once again, the part number is probably no longer valid. Do the check, and we'll go from there.

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    • #3
      And that machine is worth some effort--one of the best ever made. Mine is way older than yours, and is the nicest MIG machine I've ever used.

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      • #4
        Aeronca41,

        Thank you for responding, I really appreciate it. So, this afternoon I had some time to do a little investigation work regarding the problem. As I looked at the machine in preparation to remove the shroud, I thought, "why is that blue hose connected to the flow meter?". Sure enough, a clear cut case of felony stupid on my part. There is an HTP Powermig 200 sitting above the Millermatic 200, on a custom frame attached to the running gear of the Miller. I had the HTP connected to the bottle, not the Miller. The Miller has a black hose. Anyhow, a little wrench work, and the 30 year old Miller is still running like a champ.

        Thanks again!
        Last edited by WeldingJohn; 05-01-2021, 07:18 PM. Reason: Missing word

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        • #5
          Excellent! We have all done things like that somewhere along the line--and as long as they aren't something that would kill us, we're OK--but still feel really dumb! Glad it was so easy.

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          • #6
            Originally posted by WeldingJohn View Post
            The manual say the gas valve part number is 116-996. It can't find that part number anywhere, even on Miller's site. So, what do I do now? I don't want to give up on it, as it's in mint condition, and I've never had any other problem in 30 years.
            I know you solved the issue, but in case someone else winds up here with the same question I thought I'd add some details. Many times it's easier to find superseded part numbers on websites other than Miller's for some reason. Millerserviceparts.com shows that part number as being replaced by part number 218421.

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            • #7
              In addition to that, I’ve called Miller parts department. They won’t sell you the part, but they can get you part numbers, new part numbers and compatible part numbers.

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