Bravo !!!!!!!!!!!!! I love it !!!!!!!!!! Right on point. The hint # 3 was total misplacement and misunderstanding of the ICC MARKER black wire.
I'm guessing whoever "created" this wiring was very experienced wiring pickups and RV trailers. "I've done this many times before, don't need no stinkn' manual". In the world of pickups and RVs THE BLACK WIRE IS ALWAYS +12VDC! "I need to power the Brake Controller from the Jackalopee". Another manual "no read", where it says, "there is no power in the Jackalopee to run things". "The Brake Controller has to be powered and grounded from the semi batteries". The genius saw multiple opportunities. Aha, black wire, lets go to the +12V DIRECT, this will go to the trailer batteries and charge those, lets splice it and also go to the Brake Controller and power it. Also, there is a free ground above it for the controller, boy, my lucky day. Unfortunately, in the semis the black wire is trailer running lights, there is nothing on it unless you turn the lights on. I don't think the running lights circuit would be happy charging batteries, but no damage could be done, the instant key is turned on, the +12V DIRECT relay side is disabled. The manual says so.
Incidentally, the troubleshooting of this mess was pre-planned few days in advance, The truck owner made an arrangement with DirecLink to stop by and have Alan look/fix it. Having somewhat knowledge of what was in there, I suggested that Alan junk the "creation" and replace it with proper harnesses which I shipped to them "for the occasion". This is turning into a mini-product, just the harnesses. I have used and shipped four others already for similar situations. Jackalopee has been installed, it's a mess and we are tearing our hair out figuring it out. JUNK IT and re-harness it. One of those went to an owner who just bought the Jackalopee without the kit. The guy is really good, can find and buy anything he needs, installed the Jackalopee and ran the cables. Then he saw in the manual the pre-made harnesses. Even though he could do it, he just had to have a set. I got couple of messages, "are they gone", "did you ship them".
I'll make some pictures of just the harness set and post it later.