First, UNPLUG the Welder! There is a small control board (2"x2") that the feed motor plugs into, it has a fuse on it. Here is what you do: Follow the circuit board trace that goes from one side of the fuse though a resistor then to the connector full of wires on the edge of the board, check that resistor for continuity it should read some value besides open. If it is open, this is your problem (as the drive motor ages it draws slightly more current than new, which should blow fuse, but instead blows the resistor). The resistor should be replaced with same resistance value, if problem persists replace again but instead of 1/4amp bump up to a 3/4amp for $1 or replace that drive motor for $150, you choose. Good Luck!

NOTE: As with any circuit board, take precautions to prevent ESD damage to board.

You need to check the trigger switch wires where they connect inside the welder. Over time the tiny little wires in the cable can get stressed and break. Way less often the switch inside the gun handle gets broken or misaligned.

Regards,
Carl