Motorola 8t6a tach help

[Matt K.]

I bought this tach at Island Dragway about 2 months ago. I wired it and got nothing, popped off the back cover and saw that there is a disconnected wire. Does anyone know how this should be wired? I know as much as much about electrical as I do astrophysics. Squat

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[WV64Signet]

In lieu of someone more expert I'll add a bit to this.

Can't tell the colors exactly but if that is black then that is usually a ground.

These are from a similar model but not the same. It's an 8T8A

 

[67Dart273]

Not familiar with those IT MAY REQUIRE A SENDER. That is, "only the meter" is in the case

 

[WV64Signet]

Not familiar with those IT MAY REQUIRE A SENDER. That is, "only the meter" is in the case

It's an old unit.

I did some online searching for any instructions and came up empty for that model