I just read this post and it is perfect timing. I was coming home from a show at night and got on the gas and the headlights got bright and one of them burned out. The next day I took notice that my shift light for my tach started staying on. I did all the tests you listed and I have very low ohms and read 0 volts from the battery neg to the alt case but with a meter on the battery it reads up to 19 volts as I bring the rpms up to 3000. Does this pin point my problem to the voltage regulator?