Well as the switch still has power obviously, I'd start lookin for things going on and off lol. It could be lights or stereo component like an amp. Underglow lights auxiliary fan? A hot wire that doesn't go to anything could lead to a fire!
Yeah the previous owner Frankensteined an after market stereo into it and there were wires everywhere so it could've been a switch to the amp that was in there. I've been driving it for about 8 months and haven't had any problems with it yet