Thanks Dan, I have a DMM and checked the posts... I have 78 ohms between 85 and 86, and 2.5 ohms between 87a(center pin) and 30. 87 pin gives no reading with any combination of the others. So as I suspected 85 and 86 is the coil and I'm guessing 30 would be the 12v pos in and 87 would be the Arduino connection in the NC configuration.. when my code sends a HIGH signal to 87 it will complete the connection? Does this sound right? I take the ground from the ATX PS and connect it to my Arduino ground. I'm starting to understand but just afraid to connect it all and throw some juice into it lol.