Altenator produces 12volts. Had it tested and it passed. Electric windows are slow. With head lights on (and they are dim) radio will shut off by its self. And battery is not charging.
Any ideas? I am lost. Is there a voltage regulator on the 78 vettes?

how was it checked ?
alt should put out a min 13.6 to charge

how was it checked ?
alt should put out a min 13.6 to charge
I took it off and had it tested. Then tonight I borrowed a tester for it. It is putting out 12.25volts. Now I have put on new altenator. and it puts out same voltage.