I found the problem. The ground side of the connector to the power port got hot and oxidized to the point that it created a high resistance. Apparently, over the years the connector contact got slowly worse to until it started getting hot enough to heat the "marginal" contact to oxidize the metal resulting in a voltage drop. It even melted some of the plastic connector housing.
I just replaced it with a cigar lighter port. For some reason I had a hard time finding a power port at parts stores. I was still able to use the power port cap and it looks no different than it did before.
I discovered an advantage to using a cigar lighter over a power port. The cigar lighter has a detent device in it that holds the plug in place. The power port just counts on friction of the outside ground prongs to hold the plug in place. I have found several times when I am off-road, all the vibration can allow the plug to work back enough to lose contact. The cigar lighter port should solve that problem.
2002 FX4 Bright Red Supercab 4.0 SOHC, manual 5-spd & Tcase, 33" BFG MTs, K&N air filter, Modified air box inlet, Gibson SS cat. back exhaust, Bama flash, Hidden Hitch round receiver, Rear helper air springs, Electric trailer brake controller, Line-X bed liner, WAAG bar with KC lights and Wildernest shell.
Last edited by IN2 FX4; 10-28-2014 at 10:43 AM.