I had my generator light come on about a week ago in my 72 307. I replaced the alternator and the voltage regulator which had been the culprits in previous times when this has happened. THe light went out, however when i checked the voltage i saw that it wasnt charging. While running the charge reads only around 11.6 volts, but when it is turned off it reads around 12.0 volts. What could be causing this problem?