Mig Welder Help

adammichael · Nov 21, 2006

I have a Snap-On MM120 mig welder that I am having some trouble with.
The wire sticking out the end of the tip will arc against the metal being welded without pulling the trigger.

Does anyone have any ideas about what might be wrong? It used to work fine

warrior24 · Nov 21, 2006

sounds like the trigger button is broken, its is a switch that opens a line of current so you can weld when the trigger is pushed.

Matt Shade · Nov 21, 2006

I'd agree that you have a bad relay somewhere. You'll have to hunt up the owners manual, and hopefully it has a parts and wiring diagram.
The trigger is pretty much just a switch for a control circuit. If you take the hand peice apart you will find that it has 2 leads that go back into the welder. You might test these with a volt meter and make sure the switch is breaking the circuit.
I'd sooner guess that its the relay in the machine that kicks on the welding current. If it was only the trigger switch, then the wire feed would remain engaged as well.

warrior24 · Nov 22, 2006

ahh true didn't think about the wire staying on

leon.pugh · Nov 22, 2006

A small arch/spark is normal.

Leon Pugh

Tommegow · Nov 22, 2006

As just stated a small arc/spark is normal, think of it like static electricity.
(If it is a small disharge) I find it alittle useful for orienting the tip just prior to starting a weld

warrior24 · Nov 22, 2006

Tommegow said:
As just stated a small arc/spark is normal, think of it like static electricity.
(If it is a small disharge) I find it alittle useful for orienting the tip just prior to starting a weld

true but, are you having this problem or is it arcing alot

adammichael · Nov 22, 2006

warrior24 said:
true but, are you having this problem or is it arcing alot

It is arcing alot. If I have 6" of wire sticking out and touch the wire to the workpiece all 6" will glow and burn. I could light a cig with it ( if I smoked)

Thanks for all the previouse answers. Any suggestion to fix it would be appreciated.

warrior24 · Nov 22, 2006

just use a multi meeter and test it to find shorts

Toxey · Nov 23, 2006

Some mig welders keep the wire constantly hot.I know some of the old Miller machines are like this.
I remember when I was getting ready to buy a mig welder,Hobart specified that their welders did not arch till the trigger is pressed.That was the main selling point for me.
Whether or not yours is like this ,I couldnt say.

P.S.-- Sorry,didnt fully read the post.I now see that you said that it use to work fine.