Hi guys, I have a Murex tradesmig 135 its about 15 years old not done much welding over the years, a few bodywork repairs ie welded the lower 5 inches of a Bay window vw van a 2cv chassis, its not in regular work thankfully. My problem is yesterday I was replacing the sills on my transit and it welded perfect, great penetration and nice weld pool. I was nearly done except for 3 small holes where the metal went thin, the holes were 1 inch by 1 inch to get back to good metal for welding. I cut out the bad metal and prepped the new sheet steel, and when I went to weld I Got the earth clamp on nice new metal and it would not strike any current. all it does is spool wire out the torch, same if I strike the clamp itself. My dad said it happened a few months back and he go it going again by turning the penetration knob between low and high, it has 9 settings. Tried all that and still no weld. My question is what might be wrong with the mig welder?