I just found this great forum to help me with the he'll of s deal I just got on a S15Jimmy. So its a 1991 Gmc Jimmy SLE and for $500!!! Runs great sounds great and only 146789 miles. The issue Have found to have is that the dash doesn't work (oh noo) well the speedometer works great, 4x4 works even better but my RPM gauge, gas Guag and oil gauge isn't working. Everything is not working, not lighting up at all will post pics when I learn how to. The seat belt and brake light works and speedometer works spot on so all you guys girls all help is welcome!!

 

Your post is very confusing, please clarify... you say Everything is not working, but then mention the speedometer works. what exactly does and does not work?

From what I'm gathering from what you said (and some guesswork on what is unclear) it sounds like your gauge cluster needs to be resoldered. Happens very often in the first gen digital dashes like yours. There's a place you can find on eBay that will send you a new board for 50 or 100 bucks and you send him back your old one. Just a guess, but I'm thinking that your issue.
Could also be fuses too, but I doubt it.