Cold start up I had 14.3 volts. Drove a few miles I noticed my voltage was down to 11.9. The voltage moved between 11.3 to 11.9 as I drove 55 mph. At idle or 1900 rpm's voltage stayed low. New battery, good wires, clean and tight terminals. I replaced the alternator ? years ago. By the way I turned on my hi beams to see if the voltage would change. It did. It went up to 13.4voltage. It stayed there all the way home. Just a few miles away from were I had noticed the voltage had dropped. So, were did my voltage go?