problem with 85 lesabre limited

well i just got this car for free ( woohoo) and it has a problem. there is a battery drain somewhere. if i dont disconnect the battery while its off, it will drain. i read somewhere to go thru and disconnect each fuse and check the voltage drop between the negative battery wire and the negative post on the battery and it was about 12.66 V, never went to 0. anybody know how i could track down the problem? thanks

If you have pulled all the fuses and did not notice any voltage drop as you say, it means the mystery circuit doesn't have a fuse. Likely candidates are the alternator and starter circuits. To check these out, disconnect the power wire to them (battery should be disconnected of course for safety) and then recheck for voltage drop as before between the negative cable and the negative post.

alright i will try that, but i have one more question. if i start the car and then disconnect the battery, it keeps running, so i know the alternator is good. could the diode be bad in the alternator to make it drain though? thanks

Yes, exactly. Your alternator can be good (i.e. charging ok) but have a drain when idle.