Since your title is 'Battery disconnect switch' I assume that has been checked if the TT has one. another thing that can take out all the 12 volt circuits is the two, 35 or 40 amp fuses in the power center usually in the center.
Dale & Terri, Lulu & Tiki (our Chihuahua's), New rescue puppy Prince - Pom/Pug mix.
2013 Tundra, Double Cab, 5.7, TRD Off-Road, 4X4, Full Tow Package
2013 Wildwood T26TBSS - Sold
2000 Gulf Stream Sun Voyager M-8357 MH, Ford Trident V10 Gasser, 35 foot.