so are you saying that when the key is out of the ignition and everything "should" be "off" including the wipers...that they are still going??

if so, I would definitely replace the relay.

that gets battery power. the switch gets it after the relay. a relay stuck open would possibly cause this issue but I dont have the wiring diagram in front of me to prove that. after the relay is the switch. I would not blame a fuse as they are the "weak link" in this type of system. but who knows with the way the germs wire things. for all we know, it could be a worn contact point in the swivel in the steering wheel...or a worn spring in the wiper mechanism on the column...only testing will find it.