I had a similar issue when I first got mine as the wiring had been butchered by previous owner(s). It's a bit of a process but I removed each fuse separately and used a multimeter set on AMPS and placed across where the fuse had been (one lead on either metal piece which holds the fuse in place)to see what was still drawing current with power off. If you're not proficient with a meter you can remove one fuse at a time, gave it a day or two to see if the devices associated with that fuse were what was continuing to draw power and running the battery down. Takes time and patience for sure but does work.