Thanks for your reply. I am aware of the rpm requirement. This alternator comes in at 800 rpm, so it shows almost 13.9 v right away. My concern is that when you increase the rpm the voltage drops down to no lower than 12 volts. As soon as it returns to idle, the volts go back to 13.9 or so. What is puzzling, is that I put my old alternator back on and it does the same thing (1-wire also).