[Bricklin] Fuel gauge troubleshooting

[isensee at aol.com]

 For several years, the fuel gauge on my '75 Bricklin read incorrectly. It
would read about 1/2 tank when the tank was full and go to empty long before
the tank was empty. At random points in between, it would drop to empty but
then come back up again. Recently, the gauge started reading empty all the
time. This seemed like classic signs of a bad sender unit so I replaced that.
Unfortunately, that hasn't fixed the problem, the gauge still reads empty all
the time.

So, to troubleshoot this, I pulled off the connector at the back of the gauge.
The gauge then went to full. When I jumper this connector on the back of the
gauge to ground, it goes to empty. Putting a variable resister from the gauge
to ground, it always reads empty. So it seems like the gauge is not responding
to resistance as it should. Does this indicate a problem with the gauge? Any
suggestions what else the problem may be and how to troubleshoot it any more?

Scott