Electrical System Flunked

So far as a drain, start with a test lamp. Disconnect the battery NEG and insert the test lamp in series. If it lights brightly, and is a small lamp, try a larger one, such as a stop/ tail lamp bulb. Disconnect things one at a time to find. Pull fuses. Check the glove box/ courtesy/ trunk lamps.

Look for aftermarket "hacks" especially stereo amplifiers, etc. Disconnect the big black wire going to the alternator and see if that kills the drain. BE CAREFUL as that wire is not fused, and is a main wire, will burn smoke and melt!!! If shorted!!!