[greg64]

Here's what I know.... the gauge has 3 wires. One goes to switched ignition, one to gnd and the 3rd goes to the sender. This one is dark green, 18 gauge. The sender grounds through the engine for the return path. If you look at the back of the cluster, you should be able to identify each of the three wires, since the power and ground are used by many other things. Alternatively, if you use a meter to measure from the sender wire to ground, it should read a high resistance when the engine is cold (thousands).