Mine did the same thing. Changed the converter, problem solved. Check your converter, when it goes bright, the converter fan will come on and go off when it goes dim.
if yours is changing between coach and chassis batteries, that sounds more like a BCC problem under the hood.
If your BCC is a model 2050 from "RV Custom products" then here is the schematic and troubleshooting guide.
06 Hurricane 34FT WH W20 Chassis 8.1L 129K, Steersafe, Koni Shocks, DIY Trac Bar, Tri-Metric 2025RV Battery Monitor, 4-6V Batteries, Scan Gauge 2, Crossfires, 735W Solar Morningstar MPPT-60, KVH R5 In-Motion Sat, XM Radio, 07 Chevy Malibu Maxx Toad, Falcon 2, Brake Buddy, Escapee