Blower motor switch

All of a sudden the med and high positions of the blower motor switch won't work, only low works. I didn't have the dash open or do anything to the car, just drove it. I heard there may be a relay that went bad, but don't know if that is the problem or if the switch is bad. Any ideas?

matt i have this same problem it throws low only on mine wont switch. Have u looked at the back of yours yet? I did on mine to find that it looks as if a wire shorted out and mealted some stuff. Im trying to figure mine out now what is wrong. If i get mine fixed i'll let ya know what i did I have 2 91 mustang 5.0 droptop's pretty much both identical except 1 has different rims, no hood scoop and no spoiler.
editing mine found out mine today the switch was shorting out when switch and the plastic that melted was covering 1 of the conectors inside the harness not allowin it to switch so i have to replace mine. yours might not be that but its worth lookin at