MIG welding problem finally solved after years

I bought a 2 month old Lincoln 180 mig off CL for cheap. The guy was a "shop foreman that welded all the time" and said he didn't need it anymore cause his buddy told him he had free reign of his Miller. I took it home and fixed the polarity. Thing welds great! I am pretty sure he just didn't know how to set it up and couldn't read/google....lol