So my rear wiper worked fine on my 99 cherokee then out of the blue on day it started acting funny. I turned on the Jeep and the wiper was on but the switch was off. Messed with the switch, nothing. Kept playing with it then I made it worse. The wiper was on and it continually sprayed fluid til it emptied the tank. So I bought a new switch for it and it does the same thing. It continues to turn on with the switch off but didn't spray anymore. The only thing I did to get it to stop was pull the fuse. Is something in the wiper motor bad?

 

Either that or you have a wiring short to ground.