Close
Q:

wiper arm doesnt move but i can hear the motor running on 2000 Ford Explorer

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
whenever i turn on the rear wiper the arm doesnt move
(2) Answers
ziptie is right, it's most likely the retainer nut that holds the wiper ARM on. Just be sure the wiper motor AND arm are both in the parked position before tightening the nut, if not it might wipe the liftgate instead of the window, then it may be a stripped shaft!
There is a plastic cover over the nut you need to pop up for access to tighten it up.