Cadillac Repair: 97 eldorado, gas gauge, gas tank

Question
the gas gauge shows full with the key in the run position,but never goes down, i can't tell how much gas i have. when the key is in off position, the gauge drops to empty.
                           dave

Answer
Inside the gas tank there is a float that sends the signal to the gauge. This is maybe stuck or just plain malfuncioning, i would first check the resistance at the gas gauge, and then the wire from the float in the tank, make sure there isnt a short. If theres no short you most likely need to replace the float in the tank.