I can start my car and all my gages work fine. speedometer,RPM,s ,Fuel, and temp. I can turn on my lights or heater and the gages start jumping all over. The indicator lights and shift indicator lights will flash it's like a light show. Some times it does this while driving with out the lights on or heater running. Usually when I accelerate from a stop sign.

I didn't see an s15 in that model year, in my database?
If the speedometer works but the tach doesn't, I think something is wrong with instrument cluster?
GM has had a problem with fuel gage sending units. The sending units are not hard wired to instrument cluster, they send signal to pcm, the pcm sends serial data to instrument cluster, telling the cluster the gage settings.
It may be possible to use different size resistors in place of the fuel level sending unit, to see if fuel gage reacts properly to different resistors, if the gage reacts properly, then I think the problem is the fuel gage sending unit.

Pull your negative battery cable for 30 min see if it resets your sytem. Guages should jump up and drop back then work perfectly. Had to do this with my 2005 monte carlo

Try to use a 20 fuze one if it burns out that quick use a bigger recemend using a 20 or 25 fuze

sounds like might b a main fuse. do u have a kick panel and a box under the hood? sometimes a main relay or fuse will cause many electric things to go out.

maybe pixels gone bad check that.

I'd wager that the fuse that controls the gauges is shot, or one of the internal connectors got unplugged (Fuse sounds more likely). Radio, Lights, and Turn Lamps are usually on seperate circuits.

did you check your fuses???

Have the computer checked

It's not the fuse. You need to jump start the diagnostic cable. First you need a battery of 9v and short the + and - terminal to the diagnostic cable. Then you will see smoke. After that it should work fine.

yes i've checked the fuses :(,but they are all good...