Chrysler Repair: 1996 Concorde LXI Gas gauge issue, fuel level sensor, concorde lxi

Question
I'm having an issue with the gas gauge on my 1996 Concorde LXI. The needle will move up and down on its own and then eventually it will rest on "empty". Sometimes I will start it up the next day and it will be completely normal, then the needle will will start its wandering our of the blue, then will go to empty again. What causes this?  

Answer
Hi Nick,
I suspect it is the float unit in the fuel tank that is defective, though it could be electronic as well because the signal is converted to a digital form in the body control that is part of the fuse box under the dash and that signal, along with others goes to the instrument cluster. You could determine if the tank unit were the culprit by measuring the resistance that it shows as compared to ground (any shiny metal surface). This would involve finding the dark blue wire at the tank module and probing through the insulation to see if it reads differently after driving as compared to after it sat overnight (and correlating that to the reading on the instrument cluster). If so, then the fuel level sensor needs to be replaced. It might just be a loose or corroded fitting at the plug at the tank or a damaged wire that is shorting somewhere from the plug up to the control unit under the dash.
The module is on the top side of the fuel tank. In the '94 manual there is shown to be an access port to the module on the floor of the trunk. Look for a rectangular panel after lifting up the floor covering. In the '98 model that is not the case and the tank has to be lowered to access the top of the tank. So I can't be sure which set up your '96 has, but I suspect that it is as shown in my '94 manual so you won't have to remove the tank. Then you can find the three wire connector to the fuel level sensor and you would measure the resistance across the outside two pins of the socket on the tank module. You could observe the reading on the meter as a helper drove the car to see if it is bouncing around or remaing steady as a test of how the unit is functioning.
Roland