1996 Peterbilt 379 semi electrical issue

Good morning 12v members, long time member first time poster here. Working on 96 Peterbilt 379 w/ Cummins N14 turbo diesel. I know this isn't the typical vehicle being chatted about on here, but with an electrical issue I figured this is definitely the right group of pros. When I hook up the batteries, I have power to the dash warning lights, 3 of them on "Engine Fan, Oil, and Brake Air", I also have power to the blower motor switch - without the key in the ignition. Once I start up my truck, all the warnings lights turn off. I'm afraid this will definitely kill the batteries if left uncorrected. I've already replaced the ground cables from batt's to starter, alt to starter, str to frame, frame to cab and cleaned the two ground connections in that can that I could find (far left and far right sides behind pyrometer and glove box thinking it was some sort of ground loop, no success. Replaced the ignition switch- no luck. Replaced the main acc relay- that's when I noticed that the wire that should be hot only when the ignition is on has power even when completely disconnected from the relay. If someone can tell me where to start searching for possible solutions, I'd be incredibly grateful. I've tried to find a spot where someone may have hacked into the O.E. wiring to power something that would cause this but all seems very clean, no hacks.

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DevilDog586

Seems like incorrect wiring to either the fuse box or ignition switch, there's a live where there should only be ignition.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.