So I have a couple questions about the installation involved with my new tach. Its an Autometer Ultralite II, 5" electronic tach.

What Im looking to do is find out which wires are which in the existing harness so I can reuse them.

Looking at the large connector that goes into the back of the gauge cluster, those are the wires Im trying to decode.

For the new gauge I need 4 wires:

1) Signal
2) Lamp
3) 12V power (accessory right?)
4) Ground

So what I want to know is what wire in that large connector is the signal wire, because Im assuming I can just remove that from the connector and reuse it.

I can tell by looking at the connector that 3 of the wires contact to the circuit board and run to the 3 prongs on the back of the stock distributor. So, Id assume 1 of these is the signal and the other two are for lighting?? 1 of them runs just to a prong on the tach, and thats it....while the other 2 run to prongs on the tach and to other bulbs in the cluster.......So would I be wrong to assume that the one running to just the tach is the signal?

Yeah, so if this makes any sense and you have any input or experience with wiring these gauges Id appreciate it.

Thanks

 

You might find what you're looking for here:
http://www.nrjvette.com/johdotukset/...tte%201980.pdf