Amps don't reach preset while welding, is this right???

[Paul Moir]

If the pot is doing "funny stuff" when it bottoms out, it's done and needs to be replaced. It should go down to just about zero (55k on the other side) and stay there. If you travel it any further it should hit the pot's mechanical stop and stay at just about zero. By "just about zero" I mean say ~0-2K ohms

[joshuab]

If the pot is doing "funny stuff" when it bottoms out, it's done and needs to be replaced. It should go down to just about zero (55k on the other side) and stay there. If you travel it any further it should hit the pot's mechanical stop and stay at just about zero. By "just about zero" I mean say ~0-2K ohms

What he said. With the pedal up, you should measure very low ohms between pins 1-2 and 55 ohms between pins 2-3--or vice versa. It depends on how the pot is wired up. With the pedal down, you should measure the opposite. As you press the pedal down, 1-2 will scale from 0-55 and 2-3 will scale from 55-0 (or vice versa), proportional to the amount of travel. The values on 1-2 and 2-3 should always sum to 55. And 1-3 should always be 55, no matter what position the pot is in. If the pot deviates from these conditions, then it is messed up and needs to be replaced--but do be careful you are taking correct measurements, because pots are pretty robust as long as you don't wear them out from twisting them 500,000 times OR twisting them too hard and physically breaking them. It's really unlikely that a pedal pot would experience that kind of abuse. Even if the rack was mis-adjusted, it wouldn't have enough force (I would think) to break the pot.