About the only thing you can do is measure the primary and secondary resistances. Doesn’t really stress it or provoke faults when it’s hot. If in doubt, swap it out.
I asked this when I was an apprentice and the answer was. They either work or they don't! I've stuck with that ever since.
I have one that was OK when I first got my bus - but when I serviced it I bought a new Bosch one and put that on - it runs OK too but I still have the one I took off that I know was OK .
You could wire it up with a condenser and coil plus to a car battery positive and the case of the condenser to battery negative... and then short out the condenser and release. You will then get an electric shock from the primary and a belt and a small black hole in your hand from a big fat blue spark from the centre cap connection. That coil is good. Your hand holding the wire is the points. The hole in your hand is the spark plug.
Muir suggests the following: “Pull the center wire out of the distributor, get something really insulated to hold it, like a pair of pliers with plastic handles [ . . . ] Hold the end of the wire about 1/8” to 1/4” from a bare metal surface and have someone turn the engine over with the key. If you get a bright, hot blue-white spark, your coil is like new. If you get a good strong yellow spark, your coil is getting old but is still serviceable. If you get a weak, orangė spark that will hardly jump the 1/4” gap, you need a new coil.” I’ve never tried this.
That's the easiest way to give it a basic check although some say it will screw up the electronic ignition if you have one fitted... Never tried it to be honest , I'd just fit a known good coil Sent from my SM-A320FL using Tapatalk
