1993 Pontiac Sunbird speedo...?

[Southern Hippo]

I just bought a car, the speedo and odometer (of course), engine temp indicators dont work... the fuel gauge fluctuates, from 3/4 tank, to over full, to 1/2 tank..... Might this be a dash issue, or a speedo cable?

thanks

 

[Zimgxp]

Check for a bad ground.

 

[Loonerone]

There's no speedo cable since the system is Electronic.
Check the Wiring going through the Firewall for Insulation breaks which will cause Opens in the circuit(s) and may well be the fluctuating gauge(s) reason(s).
While you're at it, check ALL GROUNDS in the Engine Bay for anything possibly broken, loose, etc.