windshield wiper ass'y passenger side slipping on its drive shaft

usually just tightening the nut will fix the problem. if the problem has been neglected for too long the hole in the wiper arm can become elongated and unuseable or the knurls on the drive can wear off. remove the arm, clean the area and reassemble using loc-tite thread locking compound, and clean the snow or ice before using the wipers.

My Mother had the same problem. I had to clean out the groves on the drive with a sharp object, I used a triangle file I had on hand at the time I used the end of it could have used a old knife. then put a star washer on also and some used some Loctite on both the groves and the nut and tightened it.