i have a teleflex 7000rpm tacho. it has a light in it ,on the back of the gauge there is a pole for the light . i take this as being the positve conection.so where does the the earth wire hook up to for the light?
The earth (ground) connection for the light is internal to the tach and is the same as the earth connection terminal on the back of the tach. All you need is to connect the light "L" terminal to the "L" terminal on any other gauge.
Depending on the model (and age) of the tach, you may just have a bulb and socket that clips in and has 2 wires sticking out.
Could you post a picture of the back of your tachometer?
