Silly Light Switch Question

[VioletSky]

Hello all, I purchased my 2004 Montana about 8 months ago and I am wondering if anyone can help me. There is a set of 3 light switches on the left-hand side right when you come into the entry door. One controls the outside light, another controls the overhead 12v light on the ceiling. However I cannot figure out what the middle switch controls. It doesn't seem to control any of the lights or the outlets in that area, and finding an electrical diagram is impossble.