Hello I just recently started to restore a 66 grand prix.  The vehicle was in the garage for the past ten years.  I am having some issues with maintaining the proper vehicle voltage.  I recently replaced the alternator, battery, voltage regulator, and the cables.  Currently when the vehicle is running the alternator (61 amp) is only putting out 12.3 volts.  The battery is about the same.  When ever I turn on the headlights or the air conditioner the voltage drops to 11.7 when I run both it sits at 11.5-11.6.  I am not familular with this years power rating or where the voltage should even be.  Is it normal for the voltage to drop and the regulator not to increase alternator power?  I have asked countless mechanics about it and no one seems to know anything about it.  On the back of the alternator there is only one wire running out of it from the "F" position.  The voltage regulator is running wires off of the F and #3 spot.  The vehicle is set up for gauges not the indicator lamp.  There are no other wires running anywhere.  Hopefully someone can help.  Thank you  

What kind of voltage regulator do you have on your vehicle now? The old mechanical or a modern electronic?  

I replaced the one that was on there with a BWD.  I had to return it three times because it appeared as though it was not working.  I ended up swapping out the alternator for a new one and bought a NAPA Echlin voltage regulator.  The battery is getting charged but only at the voltage that the regulator starts out at.  If the car is started and the battery voltage is 12.8 then the alternator will continue to push 12.8 until you turn on an accessory.  It returns to normal voltage when you shut it off and then discharges .5-.75 volts over night.  I have to re-charge the battery once every two weeks.  Any ideas or suggestions?  

A suggestion is that you take your first regulator and remove the cover.(Mechanical) Inside you will find a pair of small contact points and an adjusting screw. This one can look different on different units. Some you can turn by hand or a plier and some with a screwdriver. Some will even have a locking screw on it. Adjust it one way or the other. (Don´t remember witch way). But be careful and screw little at the time. It can answer fast and you can get 16 volts if you take too much and damage the system. Begin carefully with 1/10 of a turn, put the regulator on the car, start and check the voltage. Adjust again and get some feeling for it. When you reach around 14 volts you´re finished.
Lock the adjusting screw if you have one and put the cover back.  

The one that was initially on the car is the same as the one that I recently bought.  There are two sets of points on the inside with a bolt towards the wiring harness.  When the bolt is loosened it raises the points further above the coil.  I did not see any kind of locking screw inside either one of them.  I will try messing with the old one and if it does not work I might just pick up an internally regulated alternator if this does not work.  Thanks again for the input.