Hello, has the small connector for the alternator been replaced? These connectors often cause alternator problems because the contacts inside them are so small. Also, have you checked the wiring for the small connector? THe following needs to be checked, make sure the orange and light blue wire has battery voltage with the small connector disconnected from the alternator. After you replace the small connector, start the truck and turn on everything that you can that is electrical. leave it on for about 4 or 5 minutes, then take your voltmeter and place one lead on the alternator battery cable post and the other lead on the battery post itself. The voltage should read less than 1 volt. If it reads more than 1 volt, the battery cable to the alternator is bad. This should get you fixed up. Thanks
The batteries are factory,so 5 years. when load tested they tested good. Motorcraft 750 cold cranking amps. This is my first time using this site, sorry for not being way more informative with initial question.