Snap On MW120 MIG Welder

Inside the gun you have the liner & the Conductor a lot of problems we find is the copper conductor fails where it bends constantly causing the current to go through the liner welding the mig wire on its way through ,I test the gun conductor by taking the liner out if possible & momentarily touching the input brass fitting & the mig tip across the terminals of a 12 volt battery to make sure the conductor is good the other way if you have a stick machine use the mig cable as the ground welding cable to make sure all the current is passing through it may involve holding the gun against the work terminal & piece of test material