Here's the process:
1. Disconnect negative battery terminal.
2. Place a 12V test light in series between the loose ground cable and the disconnected negative battery terminal.
With the ignition off the light should be off. IF the light is on, this indicates that something in the vehicle is drawing current from the battery. Lets assume in your case the light is on.
Now, with the light on go to the fuse box. Pull fuses one at a time while watching the light. If the light dims or goes out, you have found a circuit with a current "leak". Now go to your wiring diagram and by process of elimination, move through that circuit until the light is out. Problem solved.
NOW- I have the same gewnerator light issue where it gets brighter at revs. My tach acts up too, "sticking" at a couple thousand RPMs. Are they related??? I dunno. help me out!
Morrie
67 912 Coupe