I have a pivot tach and it has an adjustable redline with shift light. Do I need to hook the illumination wire to the wire for RPM signal?

This seems to be the only way I have gotten the shift light to work. There are 4 wires and I know the 3 that are power, ground and rpm signal. Just trying to figure out the illumination since when I hook it up to just dash lights the shift light does not work.

 

There is something wrong with the tach, the shift light is controlled the circuit in the tach, triggered by the tach signal, [as adjusted by you on the tach.

You should have a power and ground lead, a tach signal lead, [as you say you do the 4th lead should be tach illumination.

Does illumination work when illumination lead is connected?94