On my trailer I found an unmarked switch like that so I was turning it off and on and trying to listen for something like maybe the water pump comin off and on.. Then the wife comes in from outside and asked my there was birght lights on the rear of the trailer coming on and off. These are the two so called scare lights mounted up high on each side of my trailer...
You can see where my 8-inch scare light is located on this flagstaff trailer... One on each side...
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If it isn't your BATTERY DISCONNECT - Go check your scare lights out as well if you have them...
Roy Ken