When you pull the neg batt cable and use a test light make sure the doors are closed or the dome light fuse or bulb is pulled, otherwise you think that you have a draw down when you don't. Another thing that will trick you is a factory clock. They use a pulse to wind them every so often. On a 64 chevy if the key is in the acc position the "gen" light will glow dimly. It could also be the voltage regulator. I agree with Mitch that battery has to go, still check for a draw though. Please let us know what the tests show, I love electrical work and will help anyway that I can Jay 6155
