val fulesday wrote:

not sure what is going on BUT when you hook up the ONE wire on the coil, what is going on when you get voltage out of the other side? does that sound right or is there a possibility the coil is bad?

That's normal.  The + terminal and the - terminal are for the primary windings (the coil is basically a step-up transformer), the high voltage lead coming out the top is one terminal of the secondary windings (the other end is the case, which is grounded when installed in the car). 

What's important is that neither the - or + terminals are shorted to the case of the coil, and that the resistance between the + and - terminals is correct.  Normally you'd expect to see somewhere between 0.5 and 2 ohms of resistance, depending on the coil, between the + and - terminals when nothing else is connected to them.

If the key is on and the points are open the primary coil winding is nothing more than a piece of wire.  You put 12v on one end, you'll read 12v on the other end.  If the points are closed and current is flowing through the wire you will read zero at the grounded end because the resistance of the circuit (the coil primary) "drops" all the voltage. 

Last edited by Bullet Bob (9/19/2021 9:14 PM)