Dave66, you could try the same thing as suggested to Farmer51. Other than a voltage source, wires and their connections, the only things left are the gauge and sender. As the old wise general said, "Divide and conquer". You will also need a VOM to measure the variable resistance (out of circuit) when the gauge reads what you want. Remember also, some gauge read full when there is zero resistance in the circuit, others read empty (ex. 0-90 ohms & 90-0 ohms).
