Ford Superduty battery and charging issue

westend wrote:
Yesterday, I had my small utility trailer on the hitch of my 2003 F-250. I had dropped the trailer off and then put it back on the ball. Since it was near nightfall, I checked for running lights on the trailer. No luck. I messed with the 4X connector for a bit and finally gave up, choosing to leave the trailer until daylight. On the way home, the battery indicator and ABS indicator lit up on the dash display. I stopped the truck to inspect and barely got it restarted. I made it another two miles and the truck would not run.

This morning, I went back to truck with a fully charged battery, installed it, and made the 5 mile drive to home. All indicator lamps are now off but measuring across battery posts with engine running, I'm seeing 12.3V.

All symptoms point toward a failed alternator but this charging system has been flawless for 11 years. Is it possible that I blew a fusible link or some other circuit interruption instead of a failed alternator?

Anyone have any diagnostic tips for me?

Every Ford Alternator we've had on Mustnags, Cougars, 2 wheel drive and four wheel drive dualie diesees with twin alternaorts and twin heavy duty batteries went out in the 50 to 60,000 mile range. The diesels spin a little lower so the alternator lasted a little longer.
The same on my 05 F150 It was replaced at about 60,000 miles and is past due by experience at 191,000 unless wife had it changed and dididn't tell or I just forgot.