Dave, I think Gerald is correct, although when BCS replaced our black tank sensor a few years ago, I don’t remember the panel being removed. I guess I thought the tech got at the sensor from under the rig, but the tank bay is enclosed. Essentially the water bay makes up the streetside end of the waste tank bay. I may have simply forgotten all I saw when they took me back in the shop to show me the plugged sensor they’d removed, and they may well have had the panel off.
That said I think there’s a carpeted pop-out panel in the storage bay wall adjoining the tank bay, at the streetside end... I could be wrong, and regardless I’ve never opened it if it’s there. If so one may be able to get at things via that by crawling inside the storage bay with a flashlight. Different coach models can be configured differently, and yours may not be that way. Worth a look. Even if a storage bay panel is there, it doesn’t mean you can get at the black tank sensor that way, esp. if the gray tank is in between.
Just offering up the notion, as the water bay panel looks to be no simple removal project in itself.
Joel