My 91 sentra wipers froze to the windshield.When I turned them on the linkage or something let go.It went pop and the wipers now move by hand with no resistance.You can hear the wiper motor running. Any ideas? Thanks

 

Sounds like your linkage has come off the wiper motor. There is a little plastic piece that connects the motor with the linkage that allows it to pop off. Sometimes these can get worn, but with the ice buildup it sounds like it just popped off.

To reattach you just need to pull the splash guard off along with the wiper arms to get to the linkage and motor connection which is just a couple of screws and a lot of pop in fasteners away. Good luck with the repair.