Need help with gas gauge

[RockBit]

My ERA came as a roller, so the rear harness was factory installed. I have a Smith's electronic gas gauge and SW float type denser in the tank. The gas gauge has never worked. I went through all the trouble shooting in the wiring manual:

- when I ground the sensor wire, the gauge reads full.
- with the sensor wire connected, the gauge reads empty, even when the tank is full.

Today, I drained and dropped the gas tank, and removed the sensor. On the bench, the sensor gives 25 ohms at empty and 125 ohms at full(float up). I thought the float might be rubbing the front wall of the tank, so I bent the arm a little to make sure it clears. I hooked the sensor to the car, and watched the gauge while I moved the float. It worked perfectly.

I put the sensor back into the empty tank, and the resistance was still 25 ohms. I reinstalled the tank, put 5 gallons of gas in it. The gauge will not move.

I thought maybe the sensor screw was hitting the underside of the trunk floor, so I checked the resistance with the tank in the car ((still has 5 gallons in it). Got 25 ohms.

Does anyone have any ideas? I'm all out of them.

Thanks in advance.