on my 1992 Range Rover when we turn on the rear wiper it stays on an intermittant basis and I cannot figure out how to turn it off. If I spray the rear window, then it wil wipe and remain off, but not if I turn it on w/o the spray. it is annoying as we constantly hit this switch with our legs or hand. I have turned off the truck before to reset the wiper motor so it does not remain on in dry conditoins... not that this this is very often in Seattle. Could there be a switch issue or motor issue? relay? anyone else have this problem? thank you.