miller 175 keeps burnig wide open on its own

[mayhem148]

first i new to this site so im gonna say what up.

now for the problem. i have a miller 175 that has a tendacy to just decide to turn the voltage wide open when it wants to at times. usually when im welding something thin like body panels and stuff. when i weld something thicker i cant really tell the difference but it does do it at times. i am wondering if it is the voltage rheostat on the machine thats shorting out. im kinda curious if this is a common problem or if someone else had this same problem. i would say the machine is about 10 years old.

[richross]

I have a Miller tig welder that had the same problem. It turned out that a relay inside was worn out. Actually the points on the relay would stick closed because they were arcing. I was able to take the relay apart, sand the points and get it working again. Eventually the relay had to be replaced.

[Miller Kevin]

The voltage control pot on the Millermatic 175 is a 50K ohm, I would definately start there for t-shooting it.