i was wondering what kind of signal runs through the tach signal wire... obviously pulses, but does it pulse for each of the cylinders or only one every other revolution?
does that make sense?

thanks!

 

when I am testing my tach wire on a remote start I tap the wire I suspect and check for 0 volts with the key off, and then an AC voltage between 2-7 volts depending on engine rpm. The higher the revs, the higher the voltage. So you are correct that it is a series of pulses and that is refered to as alternating current or AC.

 

so the tachometer responds to voltage? not the pulse width/time between ignition points?

 

I need to clarify that I am an stereo/security installer and telling you what I have first hand knowledge of. I am not sure what happens to the frequency of the signal as I am willing to bet that it increases also but I do know the voltage increases with RPM from what I have personally seen. It would make sence to me that the tach is nothing more then an AC voltmeter but I do not know if that is entirely true.