The BIM should have nothing to do with the chassis disconnect at all. It's intended purpose is to connect the chassis and coach battery together for charging. I hate to say it, but could you have connected something that you shouldn't have?
2006 Damon Daybreak 3276 35'with 5 Star Tuner. 3 200 Amp Lithium batteries and 2000 watt PSW inverter/charger. 2013 Elantra on a Master Tow dolly.