Hey guys have a 97 5.4 with 145,000 miles on it. Recently ive noticed my lights will get dimmer and dimmer as i drive then get bright again it will typically do this several times in 20+ miles. So I grabbed a cigarette lighter digital volt meter and started driving last night, had lights, fog lights, radio, and defrost on when I started out I was sitting at 14.3 volts seemed normal no flickering got about 5 miles down the road and it started. My voltage started plummeting from 14.3 all the way to 11.6 then it would go back into the 14s and back into the 11s. I should note that my battery light did flicker on on the dash a few times as well when it got real low. My question is could this be a worn alternator it seems to be the alternator is original to the truck. I should also note I checked the belt and it is tight on the pulley so it is not slipping and when I put the truck in park and rev the motor the volts drop like a rock and recover when approching idle again. Thanks in advance.