You can check for parasitic draw on individual wires using a good AC/DC clampmeter like the Fluke 337. If you have shut down all of the circuits that you can and still have a draw, find the wire that has an amp draw and find
out where it goes. Some converters and (gasp) customers have modified the coach chassis from original wiring, but at some point there is a connection you can trace it to.

I would begin at the batteries first, as some branch circuits (even smaller ones) start there. Some converters even have sub-circuit panels in close
proximity to the batteries (ie: Marathon).

Contact me if I can be of any help. omnitech_nick1@yahoo.com

Nick