It really doesn't turn off, indeed. I just replaced it as it had reached its end of life and was nagging us with incessant beeps. The previous one was sensing gasoline vapors when I would fill up.
The whole electrical is a mess, I'm seriously thinking of hiring someone to redo it altogether eventually... but it's a big haul and calls for a damn lot of money. (Just to give you an idea, the wire splices in the rear bumper aren't even waterproofed. They're just connected with crimp male/female connectors, in a place that gets lots of water and mud. How does one even do this?
We're on our fourth RV (been through a 40-footer, then a fiberglass trailer, then a camper van and then this). I have yet to see something built worse. But I happen to like this bug for a number of reasons, hence the willingness to put some effort in making it livable.