If you checked the volts at the coil with the eng running then thats not bad. To do an accurate check you need to read the coil volts with the key on eng not running. Think of it like if you had points in the dist as the points do the same thing a transister does on the electronic ign. Anytime you read the volts at the coil + terminal it will read 12 volts with the key on eng not running if the points are open. Even with a 5 ohm ballast it would read 12 volts with the points open and eng not running. Now with the points closed then current is flowing and you should read about 6 to 7 volts at the coil + terminal with the key on points closed and eng not running. So when the eng is running it will read an average of the 12 volts and the 6 to 7 volts. See with the points open the voltmeter then would be hooked in series instead of paralell like it should be with the points closed and that why it will read 12 volts (battery volts) with the points open. Think of it like a garden hose with water flowing. If you put a restriction in the hose to slow down the flow you would be able to know about how much the restriction is with the water flowing out the end of the hose. Now close the valve at the end of the hose and the hose will just build up pressure and read the pressure since no water is flowing and you wont know what the restriction is. Thats kinda like what happens with the points open as no current will flow with the points open so you wont get a true voltage reading.

Let us know what it reads with the key on eng not running ? Ron