[Chevelle-List] low volts

[vmckague]

On my 64 elky I'm having trouble with the charging system.  At idle,about 750 RPM's, the gauge shows around 13.8 volts. As I bring up the RPM's the volts go down. At about 2500 I'm down to 11.5 or 12 volts. Turn on the lights or any other acc. and it goes down even more. I have tried a different alt. The alt on mine has an internal regulator. I started out with a stock alt for a 75 monte and now have a 100 amp one on it. The belt isn't slipping and I can't seem to find anything else wrong. Anyone have any ideas what could be causing this? Thanks Vernon