On the last trip I noticed some voltage anomalies as well. On the trip up, the voltage was hanging right around 12(verified with a 12v plug in digital volt meter). Had me a little concerned, but everything seemed to be operating fine, and the voltage wasn't dropping. On the trip down, voltage was right around 13.9ish the whole way.
I went out yesterday to investigate a little more. Started the truck up, took a measurement at the battery(14.3V), and the alternator (14.3V). Waited about a minute, and did it again. Battery(11.9V), Alternator(11.9V). Waited a few more seconds, and then the voltage started to fluctuate anywhere from 10.5-14.5, rarely actually getting over 13.5.
I decided to take the alternator to AutoZone and have them test it. Sure enough, it failed all 3 sections of the test. Oddly it then passed the test 4 times. Obviously I decided to purchase a new alternator. I would hate to have missed that, and then end up stranded in the middle of the desert.
