So which way is positive and negative? with the gas on clamp is negative and gun is Positive ? and with the gas off the clamp is positive and gun is negative?
Not knowing the machine I can't be precise, but I strongly doubt that polarity changeover isn't automatic. There should be a facility inside or outside the box to do it - gun positive for gas use and gun negative for flux cored wire. The changeover might even be signed 'gas/No gas'.
So which way is positive and negative? with the gas on clamp is negative and gun is Positive ? and with the gas off the clamp is positive and gun is negative?