mystery switches are always scary. You never know when one might be for the ejection seat, or the missile launcher, eh?
I've a Jeep that has an intermittent parasitic draw that kills the battery after about two days. I've gone nuts trying to track it down, without success. An ammeter shows it to be about 7 amps, and it will come on, go off after a few seconds, come back on a few seconds to a few minutes later, stay on for a minute or two, go off, on an entirely random pattern, making it all but impossible to track down. So I gave up, and put a battery cut off switch under the hood. As long as I remove the battery from the circuit when I park it, the Jeep starts instantly every time.
You might consider doing the same at least until you figure out what is going on here.
