Morgan +4 Forum

Since most older Morgans will no longer have their original coil one is less likely to find one on which the terminals are marked "CB" (contact breaker) and SW (ignition switch) but + and - instead. It likely won't make a huge difference which way the coil is connected but this article gives a pretty thorough explanation and shows how to test whether you have it hooked up in the right direction:

https://mgaguru.com/mgtech/ignition/ig104.htm

Duncan

I'm not yet convinced either way. I need to run one more experiment. A few years ago a friend of Peter J Ballard (the suspension Peter Ballard), advised that reversing the coil to keep the polarity 'correct' was actually the wrong thing to do. I ran an experiment and the results were that he was right and that the voltage was much lower with the polarity reversed because of the coil being built like an auto transformer (common connection between primary and secondary winding). The subject came up again last fall on another forum and I redid the test, with totally different results. I believe the test results were different because I used a DC power supply rather than a battery that time. A battery is not a rectifier and allows current flow in the opposing polarity as long as the voltage is higher than the battery voltage. So I will either emulate a battery for the next experiment, or use a battery for it. I need a new battery for the Morgan, so perhaps I will run the test again later this spring. Fred

(shrug) Better safe than sorry Fred. I ran across that warning on too many occasions. In any event, this far-sighted
fellow only uses digital testers now with BIG numbers..so the precaution doesn't effect ME.

gmg