I don't think the negative will be that hard to figure out. The 3 wires from the tachometer are bolted on the panel. Check the line that supply negative on the bulbs and other gauges. One of the 3 wires from the tachometer should be connected to that line. That's your ground supply.Dear all,
I purchased a very decent looking cluster with tachometer from US. Question is - how do I connect the tach? There are 3 connectors behind, all with black cables. Which one goes to positive supply, ground, and to the coil?