Well...i went looking for, or shall I say, listening for the buzzing sound from the alternator and NADDA. Started the beast up today and let it run for a bit to warm up. I then thought I would test my alternator, so I disconnected the wires from the alt. while it was running and the thing it throwing out >17 volts. yet when I reconnected it and tested at the battery terminals, I got slightly different readings at each battery. Right(passenger) side battery had 13.98V and the left (driver) side battery read 14.2V.
As for the testlight test, the first thing I did when I was doing the test was I unplugged the light under the hood. 2nd thing was to disconnect both battery NEG. terminals. 3rd (not sure if it made any difference or not) one guy mentioned holding the Neg connected long enough to make sure the electronics shut down (20-30 seconds) otherwise the test light stays bright the whole time. I noticed the light went out when I pulled fuse #2, Instrument cluster. There are 2 sepereate fuses for the instrument cluster, mine still works properly (almost) with this 10A fuse out. I say almost because it works and functions fine when the truck is running, but whenI shut it off, my trip odometer resets to 0.0, but the reg. odo and engine hour meter still keep adding up. The only other difference I notice now is that when I turn the truck off, the radio doesn`t stay on and I cant use the windows like they used to before until the door was opened.
I thought thatthis was all, but I still have a drain on my batteries when it off. So I re-tested (with the test light) again and this time there was a few things taking power. First fuse that dimmed the light was fuse #19 which powers the Vehicle Security Module and Four Wheel Drive Control Module. Now I have to find out which fo those 2 modules is the one draining power. The other one drawing power is the square pink 30A fuse top right corner, fuse #101 - Trailer Electronic Brake Control Controller. I haven't been able to find any more, but I know there is still some draw because whenI first touch the test light, it comes on and then fades within a couple seconds.
Sorry for the hugely wordy response. I just wanted to cover the steps I followed incase it by slim chance there was anything that might help you a little. This is starting to bug me that I can't find the gremlins that are in my wiring. Only fuse box I haven't dug into yet was the one behind the glovebox. I was going to do that today but had to help my 12yr old with her math homework.