Sensor for LR AC is at rear of trailer above the cabinets on the passenger side. For the BR AC, at the top front of the vanity area. Both are white, base is about the size of a silver dollar, has grille-like openings on it. At least on my '05 TK3.
Hope this helps.
And, welcome to the forum!!
2016 Tiffin 40 QBH
2015 38RSSA, traded
2005 TK3 #1869, 10 yrs of memories,
2017 F450 KR--one more Ford is it
2009 F450 4x4-died; 2010 F450-retired