A few days ago, my Starcraft Allstar minibus, built on a 2012 Ford E-350 cutaway, started having a problem that the park/marker lamps never turn off. I was originally informed of the issue by another driver on Thursday (March 31), but when I came to look at it, the lights were off. The engine started up fine when it was driven on Friday morning (April 1) so clearly the battery had not drained overnight, but the next time I saw it that afternoon the lights were on again. When I tried to start it on Saturday night (April 2), the battery was completely dead.
The lights that come on are the same as what comes on when the headlight switch is turned to the "park" position, which are also the same ones that come on as a "courtesy" when the driver's door is opened.
My first thought was that there is some issue with the "courtesy" lights feature, but that also makes the dashboard light up which is not happening here. I can open and close the door and see the dashboard lights turn on and then off exactly as they are supposed to do. I suppose there still could be an issue with this feature, but I do not know if there is any way to disable it.
My second thought was that somehow the aftermarket radio was backfeeding power to the lights, but the dashboard lights being off means that can't be true either.
I know that the previous generation (pull-out) headlight switch was known to have issues with short circuits, but I have found no reports of that for this generation's (turning) headlight switch.
I tried pulling every fuse that I thought might be relevant, but none of them helped.
I know there are a lot of places there could be wiring issues, but I'm fervently hoping I don't have to rip the body apart.
What else should I be checking?