I'm Rene from the Netherlands and own a SN95 with al electrical problem, searching for answers led me to this forum.
Allreday found a few possible solutions that i will try on the car.
Tell us more about your car, include pictures, we love pictures here.
There are a couple subforums here for you to browse through depending on the year of your mustang. If it's a '94-'95, got to the '79-'95 general talk or tech section and post any questions you have there.
If you own a '96-'98, go to the '96-'04 subforum.
You'll find a wealth of knowledge here with the people that are members. We can generally help you through any problem you might run in to.