Trying to get my tach back. '73 240Z

[conedodger]

So, I have two wiring diagrams. One is the FSM which I have two copies of. It seems that according to the FSM, there are only two wires at the coil. One comes from the distributor and goes to the negative side. It gets no more detailed than that, which is frustrating. On the laminated wiring diagram I got off of EBay, I have a green/white wire going to the coil from the tach. That doesn't jive with reality. It indicates it is for a '72 -'73 but that configuration seems to me to be from an earlier car.

There are 4 wires coming out of the harness right next to the coil. Two appear to be black with a white stripe. One is all black, one is black with either an off white or faded yellow stripe.

The car runs. It has one of the black with white wires which I found to have a 12V attached to the + lug of the coil and the single wire from the distributor hooked to the - lug of the coil. So, the other three wires are hanging in the breeze. I suspect one will give me a tach. I wonder what the others are for?

So which of these goes to the tach?

[beermanpete]

One of the black/white wires should have power when the key is on. This goes to one side of the ballast resistor.

The green/white goes from the ballast to the tach.

The other black/white wire comes from the tach to the positive side of the coil.

The black/yellow wire is for the throttle opener (I think).

To make the tach work you will need to move the black/white wire that is currently on the tach to the ballast and put the other black/white wire on the coil +. Put the green/white wire on the other side of the ballast.

If you are not using the ballast then connect the green/white to the black/white (that is currently going to the coil).