can't find source of battery drain

[dna]

My 03 has had a battery drain problem for quite a while now but I've been to lazy and busy to really tackle it. Instead I installed a battery guard which automatically cuts the battery when the battery gets low. I find this device is always cutting my battery but at least I can start my truck after hit the remote to open the solenoid again on the battery guard.

Well I finally went out today to try and find the cause. I disconnected the pos battery terminal and then put a power tester light onto the disconnected pos terminal and the other end to the pos on the battery - sure enough there was enough draw that the power tester light was on (and quite bright too).

I then pulled every fuse from the engine fuse box, one at a time, to find the cause - none made any different. I then did the same exercise with the fuses on the driver side dash area, and again none made any difference???

So now I am confused. Are there are other fuse boxes in the truck?? If not, I guess my issue is with something not first running through the fuse boxes. Being that my truck is stock (no after market stuff) does this make sense. I thought all factory electronics went through fuse boxes??

I've read that the ignition switch can ground itself to the steering column and cause a drain - would this not go through one of the fuses too? If it does not I guess this may be a good place to start - how do I test my ignition switch if it is grounding???

Thanks