what does the factory tach read for rpm signal, like the voltages...

 

I believe what you need is, is a meter that reads Frequency. Voltage readings won't cut it. Your not going to see a rise in voltage proportional to the rpm is what I'm trying to say.

You'd put the meter on Freq and put it on the yellow/blue check connector at the Trail Coil assy area of the acr. It's yellow/blue and is a bullet shaped connector open at one end.