On the GlowShift oil pressure gauge, there are four wires. The red controls the lights on the needle and dial. The yellow is the memory wire for the colors. The green is for the oil pressure signal from the oil pressure sender and the black is ground. You must connect red to a 12-volt ignition switched voltage. The yellow wire needs to be connected to a 12-volt constant voltage. Run the GlowShift oil pressure sender wire to the green wire of the gauge and the black wire should be connected to a good ground.