electrical problem with wiper, windows, int. lights

I’ve got a 1994 Eddie Bauer Explorer. It’s operated great until the last two or three months. Now, the windows, wipers and interior lights have intermittently stopped working. I’ve replaced the ignition switch, and was told it might be the GEM module, but I’m weary of replacing it unless I know for fact that that what is wrong. Has anybody else had this problem, or know what else it could be? My tech told me short of going circuit by circuit and replacing each one along the way that he was at a loss as to what it could exactly be, and our local Ford garage has no idea? Any ideas?