shift light/rpm gauge hook up?
 

im trying to put in a shift light and another small rpm gauge in my cooper, and i have tapped into all 5-6 wires in the back of the stock rpm gauge, but it isnt picking up a signal. Or one yellow wire was picking up a signal but it stayed around 9k rpms... Any ideas? or does anybody which wire is the rpm signal wire coming into the back of the rpm gauge?