Tachometer refurbish/update. What wiring will need to be done?

[Jred]

Finally got around to pulling out the tachometer and the sending unit. Found a place somewhat local to me in Los Angeles that will update the internals to run with out the original sardine can sending unit. What kind of wiring will I need to do while installing the updated tach? New territory for me. I’m keeping the points distributor btw. 

[Jred]

While dropping off the tach thee owner of the shop, speedo55check.com, shared with me that the sending unit is the same as what Dodge used in 1963-1966. For what it’s worth. I went with just updating the tach rather than keep things original. 

https://www.ebay.com/itm/123598190748?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=g7J_inXXQMO&sssrc=2349624&ssuid=t39zGBH1SlW&var=&widget_ver=artemis&media=COPY

[brad]

On the new Tach, there should be three wires.  Red black and green (usually). Red will be plus. Black will be ground, and green will go to the - side of the coil. On the sending unit you had 4 wires. A white ground, a yellow from the sending unit to the brass terminal on the tach, and a grey to + 12 volts, and the brown wire to the - of the coil. So to put in the new one, the grey will be your +, the yellow will tie into the brown, and go to the - of the coil, and white will go to the black  as a ground. 

Edited November 18, 2022 by brad

[Jred]

17 hours ago, brad said:

On the new Tach, there should be three wires.  Red black and green (usually). Red will be plus. Black will be ground, and green will go to the - side of the coil. On the sending unit you had 4 wires. A white ground, a yellow from the sending unit to the brass terminal on the tach, and a grey to + 2 volts, and the brown wire to the - of the coil. So to put in the new one, the grey will be your +, the yellow will tie into the brown, and go to the - of the coil, and white will go to the black  as a ground. 

Perfect! Thanks @brad