On our sprint cars there was no battery so we used the capillary tube type sensor for a Bourdon tube gauge. I would think there would be a 12v feed, a ground, and the wire to the sensor. If just two wires the unit is self grounding. The oil temp gauge was the difference between engine survival or destruction on many occasions. The coolant temp could range all over the scale but if the oil temp rose at all then PULL IT OFF THE TRACK.
