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My idea works slick!
I used a carbon pile resistor from an old battery tester - actually a Sun Vat 40. I mounted it in a separate box. The small metal box doesn't take up much room.
The first time I tried it, it started to work - welded about an inch, then nothing. Removed it, still nothing. The welder wouldn't work anymore. Fortunately it was at home in my shop so it wasn't critical. I'd put it on the + input lead, dropping the voltage to the welder. The cold switch blew. I don't know if that's what caused the cold switch to go south.
Sent it to RW - they fixed it.
I tried it again, but this time I put the carbon pile on the ground clamp, right by the weld. This time it was on the output rather than the input. Side benefit is it's next to where I'm welding, easy to reach to adjust it. It can even be adjusted while welding. Start the arc, adjust the heat to where you want it - fast, easy.
The ground clamp attaches to the carbon pile, then a short lead attaches to the work as the ground. So far so good - I've used it several times like that. I even used it to repair a horse corral. It was too hot otherwise.
Sorry I haven't been able to get back sooner with this - I've been laid up after my heart operation. Docs told me any electric welder would cause my new electronic device in me to malfunction (due to RFI.) They are wrong, I'm still alive! Just keep your chest away from where you are welding.
It's a variable resistance. The more you screw down the knob (pressing the carbon plates together) the LESS resistance, thus more current. But, before the arc is struck, since the current is 0, the open circuit voltage is the full 24 volts. The full open circuit voltage makes it easier to start the arc.
But once the arc is started and current flows, the carbon pile cuts down that current (and thus the voltage across the arc.)
Simple basic Ohms law. E=IR
Yes, the small box gets warm, even hot, but trail fixes usually are short welds anyway.
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