My gas gausge doesnt work in my 89 gmc sierra. How

Probably the temperature sending unit on the engine, not the dashboard.

The fuel level gage sending unit is defective, very common problem. The sending unit comes with a new fuel pump and is referred to as a module, also make darn sure you replace the fuel pump connector at the fuel tank, solder and shrink tube the new connector on, DO NOT USE CRIMP CONNECTORS.

im not certain, but i believe that the gauges are electronic. and when you were working on the radio you may have accidentally touched the wrong wires together shorting out the console. i would check the fuse cor the console.

If it is for the gas gauge, it is built in with the fuel pump in the gas tank.

pull the bed off or drop the gas tank

you can try to replace the senor in the gas but im not sure its worth a try

give it a complete tune up and change the fuel filter if that does fix it then check for a vapor lock and bad fuel pressure regulator

your right it is a problem with them but some repair shops can send them out and have them in a few days.

if it has a 4.3 liter motor a 86 to a 97 if it has a 350 motor a 81 to a 96 will work hope this helps