Here's a schematic I found by googling Bissell 8920 schematic:
http://middleeasten.bissell.com/images/schematics/8920%209200%209300%209400.pdf.
I am having the same problem. No problem taking cleaner apart. It is not going back together too easily though. I'm about to give up and buy a new one.
Hope this helps
Mary Pierce
March 2009