The battery disconnect (AKA Salesman switch) controls the black plastic solenoid on the Battery Control Center (BCC by Intellitec) that looks like this:
It "should" be mounted on the exterior side of the firewall or near the batteries. Every Damon I have ever seen had the BCC mounted "inverted" so the metal solenoid was at the bottom and the fuse markings were up-side-down.
The solenoid should "clunk" on and off with the battery disconnect.
These solenoids will fail over time, so the switch might be good (replacement not needed).
Finally, the Battery Disconnect does not totally isolate the house battery bank (like the solenoid itself is a draw) and the house battery can be drained over time without adding a real mechanical disconnect or occasional charging.