Well, first you will need to see if you are actually getting power to the fuse. Get a 12 volt test light or a Volt Ohm meter to determine that. If so, then go to the input side of the switch and test there. If no power, the issue is between the fuse and the switch. If power, test the output side of the switch to ensure it is good. Then test at the mirror, ect ect ect...
I have a 2002 ST and my mirrors had stop working. The problem was a beige w/black stripe power wire located in the rubber boot that holds all the wires running into the door and fender area. The rubber boot I'm talking about is seen when you open the drivers's side door, its located where the door hanger/adjustment is. The beige w/black stripe wire had ripped/cut in my case and was not provinding power. I taped it back together and the mirrors started working.
