I'm assuming you are referring to the red knobbed disconnect switch on the header of teh camper A frame near the battery. Looks like this.
I see you have a 2004, and around that time Sunline started putting that switch on.
If this is what you mean,
Red or O is battery turned Off
Green or I is battery turned On.
On and Off meaning connecting the battery to the interior 12 volt electric of the camper. When not on shore power, and being On, then you can use the lights, water pump etc to run off the battery. And when on shore power, being on allows the battery to be charged by the on board converter when you plug into shore 102 VAC power.
Hope this helps and Welcome to the Club
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC
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