Trouble shooting 1973 240z Ammeter/Fuel gauge. Ammeter works fine, it is the Fuel Gauge not working at all. With the gauge out I tested the car wiring harness 4 wire plug with 3 wires with a test light. With ignition off NOTHING (as expected).  Turn on Ignition. NOTHING on black wire (obvious ground). NOTHING on Yellow wire (UNIT connection on gauge) I believe this runs to gas tank. LIGHTS UP on Yellow w/Red Strip wire (IGN connection on gauge) Ignition connection. So this is normal correct? I n