Truck voltmeter was always at 14.0v, while driving dash analog voltmeter went to 12.5v. Went to local repair center and they said diagnostic said alternator failed. They changed alternator, three days later again dash voltmeter went to 12.5v, used handheld voltmeter across battery while running and also read 12.5vdc. When you first start truck alternator would output 14.3vdc (hand held voltmeter across battery) after 5 minutes would go to 12.5vdc.

Auto repair installed another alternator, good 14vdc for three days. Then again first start up 14v, after 5 minutes across battery with VOM 12.5vdc. Removed negative lead for 10 minutes, restarted truck, alternator output 14vdc for four days around 240 miles. After 240 miles again startup 14.v, 5 minute running 12.5vdc. Again disconnected neg. battery terminal, again fixed for 200 miles. As usual dealer has no fix and looks at me like i am crazy.