Quote:
old-fart wrote:
I have two ignition knobs on the back of my speedo. can i take the loop off one of them through the tacho to the black white trace wire?
thanks for the help so far my car is running again.
If it is ignition 12v you can use it. But you should not connect the other end to the coil positive (if you have points ignition) you need to connect it to the ballast resistor 12v side. ( it will work if you connect it to the coil but your points will burn out quicker )
ddgonzal's pics and link explian it simply;

* B - ground - to back of Instrument Cluster
* YR - IG power - to back of Instrument Cluster
* RG - lights (two lights, two wires. Not shown in photo above) to back of Instrument Cluster
* BW - signal loop - to BW wires in dash harness
The BW loop of wire is the current induction coil. The ends, logically speaking, go in between the IG terminal of the ignition switch and the single-terminal (non-coil) side of the Ballast Resistor.