Issue with millermatic 211 short near roller.

[romesnow101]

I was welding yesterday with my millermatic 211 unit is a few years old but mostly used for home and light auto use when my wire feed stopped. I opened the cabinet and found my wire shorted out near the feed roller. What is going on here do I just need a new liner?

[romesnow101]

heres a closer photo

[Aeronca41]

I don't know enough to say for sure, but it appears to me the only way for that to happen is if the liner gets shorted to ground. I wonder if there's a ground wire going to the switch in the gun to actuate the weld relay and somehow that wire got shorted to the liner? Perhaps a connector to the switch came loose and the wire touched the liner? I would cut the wire as close as possible to the liner then check resistance between the liner and the work lead terminal. Bet it's very low, and should be infinite. Perhaps someone with direct experience (far better than my guesses) will join in. Anxious to learn the real answer.

[romesnow101]

Well a replacement liner is cheapest, I appreciate the response. I'll start with a liner and post back in a bit when it arrives and is installed

[Aeronca41]

I just fear that whatever's wrong might instantly ruin your new liner also. Would be good to do the resistance check before removing the old liner.

[LoganpClayton]

Logan A.K.A Wolverine here,

I am a certified Miller, Lincoln, Esab, Themal Dyn, Themal Arc Technician and would be happy to help you with this issue. I have seen this quite a few times, the most common cause is that the insulation on you're welding nozzle has failed due to the constant heat-up/cool-down it see's in it's life cycle. The stock welding nozzle comes with a teflon style liner on the inner surface of the nozzle, or, crimped between the brass inner, and the protective outer shell. Firstly, replace that nozzle, if you want to check to see if the liner is functional, undo tension @ drive roll housing, lay gun straight, then proceed to pull (by hand) wire through the gun/liner assembly, this should be without little to no drag.

Picture of a good nozzle (note the inside of the nozzle, THAT's what keeps the liner isolated from the nozzle.):



Let me know how it turns out!


- LPC

[Aeronca41]

Logan, thanks for the info. Knew there had to be a short somewhere but didn't know the likely place. Good info!

[romesnow101]

You guys have been an awesome help I'll start with that and let you know

[Miller Kevin]

romesnow,

The weld current is supposed to transfer to the wire at the contact tip. It looks like in this case it is transferring at the drive roll instead and there are only a few things that I know of that will cause this.

1) Poor connection where gun plugs into the unit. Pull the gun out of the unit, clean the brass pin and inside the aluminum drive housing where it slides in with some emery cloth or a scuff pad. Corrosion in this area can cause the issue you are seeing.

2) Incorrect contact tip size or loose contact tip. Verify the correct size and that it is tight in the diffuser.

3) Failed mig gun. If the cable hose pulls out of the crimp or frays badly on either end of the gun it can cause this issue. If numbers 1 or 2 don't correct the issue then I would suggest replacing the mig gun.

Kevin

[romesnow101]

Well I ended up putting a new nozzle on and it ended up taking care of it. I already ordered a new liner and defuser which will be here in a day, I guess it's for for that mainly anyway. Just wanted to thank everyone who responded and great info from Logan. Thanks again guys, happy welding!

[Meltedmetal]

If you haven't thrown the nozzle far away already, did you check for continuity between the inside brass liner and the outside sleeve just for fun?