I have to disagree with the remount the wiper advice. There are two possible problems here. If you do a search on the subject you will find the answers you're looking for. There is an electric component that heats up and stalls the motor with the extra current draw of an older wiper motor. A fix is listed either here or at mbnz.org. The second is the cam has jumped a notch. Either way, if the wiper does not return to park, it will puke all you washer fluid out in short order as the headlight pump runs until the arm is back to park. (There are two pumps in the washer res. you be well advised to unplug the one for the lamps until you get them fixed)