89 Century Buick gas gauge

I have this century buick in perfect condition but sometimes the gas gauge doesnt like to work, it goes from half a tank to full. I belive its just the gas moving around in the tank, I was just wondering if anyone knew how i could fix the sensor in the tank to have the exact about of gas or around.

If somebody could help i would greatly appreciate it.

Thank you
Ben

Drop the tank and check the wiring, it may have been chafed. Otherwise you will have to replace the sensor.

My 87 Century had same problem, dealer replaced sending unit assembly (the float part) . First time, was inaccurate. On refitting, was OK, something about orientation of float in the tank. I didn't know tank was under back seat. This is second fuel pump, first replaced under 36 month warranty due to noise. You might consider replacing at this time, might not cost much labor since your already there.