Ok treading a fine line of what wiring and device was installed by Spartan and what was a Fleetwood install and exactly what the function of the device is .
Would you be able to post a photo of the device your checking ?
Could be your looking at a coach battery disconnect solenoid or even an manual reset 12 volt circuit breaker.
Does your Battery Control Center , look like the picture below ?
If so this pdf on BCCs maybe of some help.
Can you connect a jumper cable across the device and have everything 12 volt operate?
Sorry about asking for your coach's year ; you posted your chassis year and I should have clued into that .