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Thread: MTS 251si No Arc

  1. Unhappy MTS 251si No Arc

    I'm hoping someone can give me some ideas on getting my the TIG part of my MTS251si welder working. I've been having issues with this machine for a while but not it's to the point where it will not strike an arc in TIG mode. I've had this machine for several years (no longer in warranty) and never used the tig function until a few years ago and really started using it in the last 8 months. It was to the point where it would arc on the first try 7 out of 10 times and now it's to the point where it won't arc at all on HF start. It acts just like if the ground is not connected/grounded and will just keep buzzing. I have probably read every post on this topic that's on the internet and also similar posts on other brands. I'm hoping someone here has had a similar experience and can point me in a new direction or hopefully someone who has gone through the same thing. Here's the list of things I've done:

    Lift start works most of the time
    Adjusted the HF points gap several time from .040 to .022
    New ground clap, used ground clamp set from another welder
    Grounded directly to what im welding
    Tried different machine settings, 1sec pre flow, 5sec post flow
    New torch internals/parts, went back to the original OEM torch internals/parts
    New tungsten, blue and ground to different angles ect.

    I have the machine open and looking for anything that may have been loose or burnt components but so far I have not seen anything obvious. Plugs all seem fine and connected ect. I cant see everything on the main board since I don't have it all the way out. All the main wire lugs seem tight. I'm not sure what the issue could be and hoping someone can give me some ideas.

    Thanks in advance!

  2. #2


    Point gap should be .035" Make sure torch is in Negative. Replace work clamp cable as well. Preflow will delay your arc start. Keep that in mind. Make sure you aren't too close to your welder and the fans are blowing gas off your weld. Make sure it is 100% Ar.

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