Dakota Gauge Problem

I have a 94 Dakota and the fuel gauge doesn't work properly, it has been this way as long as I have owned the truck. (March 2010)You start it up and the gauge doesn't move at all or it goes all the way to full and is accurate to a half tank and then just quits working. The other day I was at the Pick N Pull and grabbed the fuel gauge out of another 94 V8/Auto truck along with the printed circuit board. Got home swapped out the board and the gauge, noticed the original board looked like it had quite a bit of oxidation and the soldering wasn't as good as the junkyard board and there was rust in spots. I did plug the connectors in with the key in the on position. Gauge went to 3/4's full and just stopped, this seemed reasonable until I turned the key off and the fuel gauge and the oil gauge stayed put. The battery gauge dropped, the temp gauge stayed but I believe that is normal until the engine cools down. After this I swapped the old gauge back in but left the junkyard board in place. Plugged the cluster back in key off this time same result. One last thing I removed all the lights and didn't have replacements (doing that today) could not having the lights installed not make the circuit complete or are the a separate circuit? (I didn't look at the board that close.) How do I fix both the new problem and then the old problem?

All the gauges should drop to zero with the key off. It sounds like you have a bad sender in the tank rather than a gauge problem.

The fuel gauge in my 93 Dakota takes forever to drop once the key is shut off. My 90 was the same way. When you shut off the truck, the gauges pretty much stay in the same location for several hours afterwards, then all of a sudden they are at 0. (everything except the oil pressure gauge, it drops instantly when the motor stops.)
Gene