Rear Wiper Motor

Question my rear wiper dosen't work, when i flip the switch, nothing moves, there is a sound coming out of the wiper motor, but the rear wiper dosen't move, any ideas?????

It's probably siezed up from lack of use. It's quite common in the older XJ's. What year is it?
I got mine rear wiper on my 87 to start working again by loosening it up with some WD40. Whatever you do don't just leave it on because you'll burn up the motor. If it's still humming, it's trying to work. Once it goes quite, it's dead.

If it sounds as if the motor is actually running, it has probably stripped the gears inside, which is the other thing it might do if the shaft seizes up and the motor doesn't burn out first.