DIXCO steering column tachometer

[1937 LaSalle coupe]

Just picked up a DIXCO 3.5" tach at the local fleamarket today. It has 3 wires coming out of it. The wires are black, white, and green. Does anyone out there remember how these wires hook-up? Without opening the tach up, the black and white wires give the lowest ohms and might assume this is for the light inside. Maybe the black wire is the ground, and the green goes to the distributor... Anybody know for sure?   Thanks.... John Lehman... CLC # 26365...

[Classic]

Does this help?  http://www.detroithorsepower.com/forum/index.php?topic=3589.0

[D.Yaros]

John,

I know not on what ride you are planning on installing this tach?  I would only point out that "back in the day" a Dixco was purchased by folk who could not afford a real tachometer from SW or Sun.  It might look a little out of its environment in a Cadillac?

[TJ Hopland]

That other site suggested that one wire went to the + of the coil.  That does not make much sense unless it was a + ground system.  The actual variable tach signal would have to come from the points side of the coil which would be the ground side of the system so a neg ground system it would be neg and a pos ground system it would be the pos.

If it was a neg ground system one wire would be to the - of the coil.  You would then need a pos power source from somewhere.  If there was a light you would also need a ground and power for that.    With a light and 3 wires the body would have to be ground for the light function. 

Do any of the wires give a reading to the body?     If its got a light is it replaceable?  If you remove the light can that give you a look inside or at least access to the light terminals to determine which wires go to it?