Hi Alvin (or do we all call you eh Chipmunk now),
Don't know if I can add much to the fuel gauge discussion, but I've been wanting to tell you thanks for the great write up on your visit to the Pacific Northwest. But to stay on topic...
There are two electromagnets in the fuel gauge. One pulls the needle toward empty and the other toward full. When the tank is empty and the sending unit drops down, current flows in the circuit that powers the electromagnet that pulls the needle toward empty.
As the float is raised up and resistance increases in the sending unit less current flows to the electromagnet pulling the needle down and more current flows to the electromagnet that pulls the needle toward full. It's kind of a balancing act.
So if you hook up power to the fuel gauge and very briefly ground the gauge cluster (without the sending unit connected) the electromagnet pulling the needle up will (should) read full. If you power the gauge and very briefly ground the sending unit terminal the electromagnet pulling the needle down will be fully operational and the needle will register just a tad bit up from empty.
Best of luck.
