I have a 2005 Fleetwood Excursion 39S and my "Main" and "Auxillary" disconnects are located in the BCC box (Battery Control Center). The BCC is located to the left of my Xantrex Inverter/Converter mounted on the bulkhead. Once you take the cover off (make sure all power is disconnected, along with the batteries) you will see a circuit board with a ton of fuses and wires. You have to disconnect all of the wires (take lots of pictures) and then remove the circuit board (it has a few screws holding it on). The two "relays" are directly behind the board. My "Aux" relay failed in the open position, meaning it wouldn't stay "closed" and my house batteries were always disconnected. I made a small block of wood to wedge into the relay holding the contacts permanently closed and then installed a physical disconnect to the house batteries.
Let me know if you can't find it and I'll send pictures.
2005 Fleetwood Excursion 39S 350 CAT
Tow: 20' Boat (Summer) 16' Dirt Bike Trailer (Winter)