this is a 68 chevelle.gas guage reads full all the time.put on the lights and it drops to empty.
i found the ground wire to the tank and sanded the wire and reattached,same thing.
when i unplug the tan wire and ground it it drops to empty,so i don't think it's the gauge.
i also ran another ground to the dash,the left side dash light was dim and the light by the gas gauge was bright.i now have bright dash lights.
any ideas where to go from here?thanks buzz

Check the grounds on the rear harness for the lights. It also sounds like the sending unit is open and needs repalced.