Please consider buying a HELM. You need the manual for any DIY repairs.
If the Defogger indicator lamp comes on, but the defogger does not work, check: (1) 40 amp fuse in the underhood fuse relay box (2) Defogger relay (best guess) (3) Perform a grid function test, and (4) Check the switch. Could also be the ground.
The troubleshooting chart can be found on page 23-247 of the 1992 Cpe Service Manual.