I have only come across one tach failure- I've got one where the movement is stiff. I don't know if it's got something stuck in it, or it's been bent or mishandled. In any case it seems to stick when revved to 2500 or above, and stay there until gravity, shock and vibration make it come back down.

I'd finish the install, and plug the wire in. The white/red stripe wire goes to the terminal at the bottom of the tach. If there are two terminals side by side, use either one, as you'll see it's part of the same piece of metal.

The three terminals at the top of the tach are for the 3 pin wiring harness plug to teh small clock. If you didn't get teh small clock, search ebay or that same junkyard. Yeah, I spell teh like you all teh time.
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