9v at Ballast Restor (pic)
Of course it reads higher unconnected. You are experiencing "Ohm's Law." What you have is the battery, and harness (the source), the ballast resistor, and then the load........the ignition system. With no load there is no current, and therefore no (or little) voltage drop. With the ballast unhooked, you still have the load of the VR and alternator field. If you unplug the VR connector, it will probably go higher yet
If you don't have one, go over to MyMopar and download a service manual for free
Then read this article by MAD Electrical:
http://www.madelectrical.com/electricaltech/amp-gauges.shtml