Chrysler Repair: fuel guage indicator fluctuates, resistance element, variable resistance

Question
I have noticed that while driving my fuel indicator guage flucuates from full to empty and then the gas light sounds off. Then it quickly goes back to full.  Can you tell me what is causing this to happen?

Answer
Hi Janice,
It probably is either a loose electrical connection in the wire that runs to the fuel level float sensor located inside the fuel tank or it could be an malfunction in the variable resistance of the sensor unit itself. The former could be remedied without removing the fuel pump/sensor from the tank, while the latter would so require. You didn't mention which vehicle/year you have so I can't tell you about how to do those tests, but basically when the needle drops to empty/warning light goes on it means that the electrical path to and thru the sensor to the electrical ground return path to the battery has been interrupted. If this happens regardless of the known level of fuel in the tank, then I would suspect the wire or its connections at either end, whereas if it is confined to when you have a full tank, a half-tank, a quarter tank, etc. but is otherwise OK at other fill conditions then I would suspect a discontinuity in the variable resistance element inside the tank which is what the sensor is constituted by that is the problem. If you want to let me know in more detail about this aspect and tell me the specific model and year then I can give you some better idea as to what would be involved in repairing it.
Roland