Oldsmobile/Buick Repair: battery keeps draining when car is off, oldsmobile delta 88 royale brougham, oldsmobile delta 88

Question
I recently acquired a 1991 oldsmobile delta 88 royale brougham from a family member. After a few weeks the car died one morning out of the blue. I jumped the car off of my mini van and went on my way. Ever since that day i noticed that the battery refuses to stay charged after i shut the car off. If it sits for 8 hours my battery meter will read close to 9 volts rather than 12 and i will have trouble starting the car (I check to make sure it has 12 when i first shut the car off). I replaced the battery and the alternator and i have checked everything to make sure it is off, interior lights, trunk light, headlights, hood light (disconnected my alarm from the battery as well). I even went so far as to shut off both my aftermarket stereo and air conditioner every time i shut the car off. These things have helped but i still have a drain. Is there any other electrical device i might have missed in my search? Or perhaps another cause that might lead to a drain on my battery when it sits?

Answer
Hi

First you should make sure the Alternator is charging while it is running. Should put out between 13.5v-14.5v. (you should purchase an inexpensive digital voltmeter)If not, make sure the alternator small wire is getting hot, and make sure the large wire is hot at all times.
Check the fuses, Charge fuse. Check fusible links. Remember also, the alternator is NOT a battery charger. It is a battery maintainer. It will slowly charge a battery, but that is NOT what it is designed for.
If you feel you have a draw, You'll need to check the amperage draw (parasitic draw) on the system.
You'll need a digital volt meter that has an ammeter on it.
You'll need to unhook negetive battery cable and put ammeter in series with battery (on voltmeter lead on negative battery terminal, one voltmeter on negative battery cable end).
Then DO NOT open doors, anything electrical for about a minute.
then see what the amperage draw is. SHOULD be around 0.025a
or 25ma (a quarter of an amp) OR LESS. If it is more you have a draw.
Just start unplugging fuses one at a time until the draw goes away (down to oem specs).(Dont forget if draw does not go away, put fuse back before unplugging another) Then you've found the ckt that has the draw, just find the loads on that fuse and unlug them one at a time.
This is how you find a parasitic draw.
If more assistance is needed, please feel free to ask.
Just advice from experience.
Good Luck