You've likely already checked to make sure you have power at the switch you replaced. The only other thing that comes to mind is that the mirrors (at least on my 2004 Explorer ST) are collapsible (they'll fold back toward the front windows to lessen the width of the truck). I suspected that if either mirror isn't in the fully extended position, the adjustment wouldn't work, but just tried the theory on mine and the mirrors are still adjustable. Sorry.
