I've seen old threads on the issue and thought I'd post my fix. Both windows on my sc weren't working so I started trouble shooting and found the problem to be wiring in the door jamb. Here's a vid for the repair. Hope it helps someone!

 

Yep! Had this issue on my 1995 SC400. Thought the switch and regulator was bad. Replaced both before digging into the harness and finding a previously soldered wire that had been broken.