Ford: 2002, F250, ALTERNATOR, ground straps, powdery substance

Question
WARNING LIGHT COMING ON/OFF FROM TIME TO TIME, VERY ERRATIC, ITS A 110 SYSTEM, I TESTED IT WITH NO LOADS & SHOWING 13.80 VOLTS, IS THE ALT. GOING BAD?

Answer
more likely a loose connection somewhere, check all the electrical connections for the charging/ starting system, Battery terminals, Solenoid, ground straps, alternator. make sure the battery is not cover with verdigris, a greenish white powdery substance that impairs electrical contacts, more likely i think due to it being erratic it is a loose connection somewhere in your electrical system