Chrysler Repair: 91 5th Avenue electrical draw, bright illumination, vanity mirror

Question
91 Fifth Avenue 3.3. Loses charge and will not start after about 3 hours. Battery and Alternator good. Did some basic troubleshooting and with fuse #12 removed battery charge loss fixed but now no radio, interior lights, and Body Control Computer functions gone. How do I quickly and easily divine which of the many items powered by old #12 is causing the short? All interior lights and radio seem fine with the fuse installed.

Answer
You've done the only easy part and even that wasn't so easy.  Fortunately, you have narrowed it down quite a bit and I do appreciate that.

Fuse 12 feeds the ignition switch halo, power to the BCM on pin 16 (18gauge pink), the electronic instrument cluster (if equipped), glove box light, radio, courtesy lamps, reading lamps, trunk lamp, vanity mirror lamp, and a few other little options.

Now, something to understand about a BCM is that it is "Awake" for about 3 mins after you shut off the car.  If you've done a draw test using a test light and mutli-meter between a battery terminal and the corresponding battery post then you'll see this expressed as bright illumination of the test light hopefully followed by no illumination.  A draw typically is indicated as a dimly lit light.  The test light is there to absorb the load to prevent from popping the fuse in the meter and the meter is there to actually measure the load.  

In addition to that ANY component that is tied in to the BCM such as the components listed above and then some will keep the BCM awake indefinitely.  So not only is the light or whatever that's left on causing a draw but an awake BCM is too.

You can determine if it's awake BCM by pulling out the M1 circuit wire (that pink 18g wire) from the backside of the BCM connector.  That will tell you if it's the being BCM awake or another component being left on.  

Additionally, the BCM is located in the right kick panel.  Most were wrapped in plastic but as easily as they keep water out they can also allow it to be trapped.  I'm going to go out on a limb here and say that you've got a bad BCM but you should still consider all of the other components still on the circuit after the fuse and unplug as many as you can, that are easy to get to.
Doug