Air pressure switch question for my welder

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Will be putting an air compressor on my homemade portable welder and bought a normal 110v pressure switch, it has 4 terminals that I can wire up.  I should only need to use 2 terminals correct? A 12v power source to the one terminal and then the other terminal to the eclectric clutch wire on the compressor.   Not sure which terminals to use for sure.Am I correct?
Reply:180 views and no input into this topic?  Its weird, somesdays you could throw a dead cat through this forum and not get a repsonse. lol
Reply:I've read this twice now and have absolutely no clue what in the world you are trying to do here. You talk about 12v and 120v. and a "portable" welder ( which says gas driven to me). Huh? All the gas driven welders I've ever worked with use unloaders. The compressor runs full time, but at a reduced rpm and the compressor vents thru the unloader when the cylinder doesn't need any more air. As soon as the pressure drops the unloader closes and the unit brings the engine back up to full throttle to build pressure. It's a purely mechanical unit. No power required on the ones I've worked on. I guess they might have some that use an electrical solenoid and sensor to control the throttle today, but they'd still need to dump the excess gas some how.The electric compressors are all simply switches. When the pressure drops the switch closes and the motor kicks on. When full pressure is reached the switch opens and shuts off the power. Switch would depend on if it is a 110v unit or a 230v unit. Never opened up one of the cheap 12v lighter compressors designed to simply inflate tires. My guess is they work the same though.In your blurry pict I see what looks like "line" on one set of terminals, and "motor" on the 2nd set. I'm wondering if it's really a 110v unit and not a 230v one myself. That would explain the 2 sets of lugs, one for each of the hots in a 230v system. Did the unit come with a wiring diagram per chance? Most usually do.I have no clue what in the world you are trying to do with what ever you have.Last edited by DSW; 02-26-2012 at 05:47 PM..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:You should be able to use 2 or 4 either one. All you have to do is (break one side of the circuit 2 terminals), to make it work, but you can also (break both sides 4 terminals)if you choose. If using 120 volts, & only breaking one side, break the hot leg. Since you have the ability to break both sides, that is what I would do. The Line terminals come  from your power source, & the Load terminals or Motor terminals go to your air compressor.Last edited by lstilts; 02-26-2012 at 05:58 PM.Reason: Spelling
Reply:Sorry, I misread 12 volts as 120 volts. If using 12 volts you can either break the positive side, (if only breaking one side) or positive & negative ( if breaking both sides). Either way, Line Terminals are from the power source, & Load or Motor terminals are from air compressor.
Reply:I am running an AC compressor, a york 210, on my homemade portable welder, it has an electric clutch, I will be using the pressure switch to kick the compressor in and out.  Ok I thought I had it right lol