Help! Slow Battery Discharge

EASY. Get yourself a 12V test lamp and a multimeter that can measure current. Most "decent" multimeters have a mA (milliamps or thousand'ths of amps) as well as at least one large scale, either 10 or 20 Amps.

Disconnect the battery ground, make sure everything in the car is off, including any LED's (theft alarm?) or other accessories

Insert the 12V lamp in series with the battery to ground. This now becomes a current indicating device. Shade the lamp and see if it glows. This will show that there is a drain.

Pull the trunk light switch if used, check the glove box light, remove the lighter and toss it in the ashtray. Double check that everything is off.

If the glow level has not changed, remove the fuses, one at a time, checking the lamp at each fuse.

Next remove the alternator output wire from the alternator stud and tape it off, and recheck.

If no difference, do you have a stereo amp, or a radio that is hot with key off? If so unhook it or remove it's fuse. If you have a modern radio with a "memory" power wire, unhook that as well.

From here on out, it's a matter of usin' yer noggin and THINKING "what is" hooked up "hot" to the battery. Unhook the battery line to your MSD. Cast a suspicious eye to ANY accessory you've added which may have a hot lead --- GPS/ cell/ other charger? Any added electronics?

If you find something which causes the lamp to go to a very low glow or "seems to" go out, now take your meter. Since the lamp is now not glowing, hook the meter up for the highest AMPS scale for safety, and see if you get a reading. If not, or the reading is nearly "off scale" on the low end, now hook it for ma (milliamps) at the highest ma scale, and see what you have.

If you don't know how to set your meter, post a clear photo of it and the model number, or at least the meter's model number, and we can help you from there.

65s did not have much in the way of mystery safety modules, so there is just not much there.

THE OTHER THING is that you might just have a crappy battery. If you cannot "see" any drain, either with your lamp or meter, CLEAN the top of the battery very well, charge it up and if possible, check it with a load tester AND a hydrometer, and then let it sit disconnected for awhile, and see if it goes down on it's own.