If you have a workhorse chassis, check under your hood. Drivers side, look for a black box that has a sticker that says "RV custom products". Take the cover off and under the circuit board are the aux and disconnect relays. Follow your chassis battery positive cable, one positive wire goes to the starter and one positive wire goes to your Battery control center "BCC".
06 Hurricane 34FT WH W20 Chassis 8.1L 132K, Steersafe, Koni Shocks, DIY Trac Bar, Tri-Metric 2025RV Battery Monitor, 4-6V Batteries, Scan Gauge 2, Crossfires, 735W Solar Morningstar MPPT-60, WG T4 In-Motion Sat, XM Radio, 07 Chevy Malibu Maxx Toad, Falcon 2, Brake Buddy, Escapee