When I strike an arc with my miller 180SD sometimes the amps start out wide open.You can break the arc and try again and it may the decrease to the amps it is set on and weld perfect. A miller repair person suggested it may be the haldivice or something like that. What do you think?

Check your foot controls first the POT my be acting up change it out w/another if you have one,

I spent today working on my miller syncrowave 180SD, with a similar power issue.

Before I go any farther, this is a job for an experienced service technician, so if you are not absolutely sure how to be safe around this serious lethal power, do not attempt to repair your welder.

The "Hall device" your Miller rep told you about gives feedback to the control board which regulates the power at the tungsten. It is a current transducer that has +&- 15VDC inputs and mine outputs 2VDC/100amps to the control board. I do not know if they are the same in every Syncro 180 SD but mine is a part # 191941 and is located behind the right side cover as you look at the front of the machine. It is a blue plastic block attached onto a copper buss bar and has a 4 pin connector on it.

If you unplug the machine from power, disconnect the 4 pin connector, then plug your machine back in, then your machine will only run at full amps, so you may simply have a loose 4 pin connector causing your problem, but I would expect that the hall device itself is failing like mine did.

I ordered one from my local welding supply for $58.00, which was actually cheaper than any I could find online.

I hope this helps with your issue.