im trying to troubleshoot my non working tach. i learned that the tach is a blue wire. I followed the wire out the firewall. there r 2 blue wires one goes to distributer which i know is the tach wire. but this is another blue wire i dont know what it is. its not connected to anything.... thanks

 

thats for a tach but mines never been connected and it works. Thats what ricers use when they install there monster tach's.

 

ooo haha thanks

 

its used for an external tach, when your doing underhood work. like adjusting idle and whatnot.