Just unplug the wiper motor. If the fuse no longer blows, the motor is shorted. There's a large plastic gear with metal contact strips around it. The spring-loaded contacts can overheat and melt into the plastic. The next time you turn the wipers on and that gear starts to turn, it tugs that contact and bends it upward where it touches against the cover plate and shorts that circuit.

If the fuse still blows with the motor unplugged, I have a troubleshooting trick that will avoid blowing more fuses. Relays do not short. In rare instances the contacts can become pitted and stick together, but that just means they stay turned on. That's not the same as "shorted" and will not cause a fuse to blow by itself.