wiring aftermarket tachomete

[jondee86]

Generally speaking, most decent aftermarket tacho's can accept
5V square wave, 12V square wave or voltage spike inputs. If you
take the signal directly from the coil, you need a tacho that can
accept a voltage spike input, so check the tacho data sheet.
Square wave outputs are found on later model cars, and originate
from the ECU or igniter module.

Cheers... jondee86