2004 chevy van, parasitic load

Left the key on overnight (I had turned it on accessory to put it in neutral to do other maintenance). Now I have a 1.8 amp draw that kills the battery, arcs the cable when I hook up the new battery. Lots of hots in the under hood fuse box when the key is off and the accessory power is off. I suspected a control mod, but I pulled all fuses, only thing that I found to kill the draw is the load side of the mega fuse. Pulled all fuses under hood, load is still there. Unhooked the alternator wiring, nothing. It's a conversion van... Thank you in advance for any other ideas.

1.8 amps is not out of the norm for the first 15 or 20 minutes.   Once the BCM goes to sleep the current draw falls way off. My thought is this past battery drain killed your battery.

Load bent a battery plate it won't charge now so say goodbye to it.

Thank you. I agree, and changed out my battery but am hesitant to hook it up as I don't want to kill the new one too. I will hook it up for 2.5 hrs and see if the load goes away. Seems odd to me to have all those fuses in the fuse box hotted up if the key is off... Thanks again, let me know if you have any more ideas!

Stuck ignition switch?

You disconnected the power cable (B/B+) to the alternator (not just the small wires eg, D+ or connectors)? If so, disconnect the starter heavy wire and see if that stops the discharge.

Cycling the ignition to accessory and on seems to work as intended with turning on and off the different options- radio, fuel pump, blower motor etc. Yes I tried both the alternator plug and the big wire. Appreciate your ideas!

I'm thinking now it was "just" a bad battery. After about 10 seconds the load goes down to .04 amps. Unhooking the trailer brake controller (small green light) and it drops to .02. I'm good with that. I've referenced this forum for years but never posted, thanks all.