Cleaning the black water tank

Also, because the tank always has a bow or low spot in it, it will always look like it has liquid in it. (Edit, I see that was covered in the last post) The gauge reading full is probably due to toilet paper stuck on the sensors. Once you get the tank flusher working the gauges should read correctly. All they are is terminals that provide an electrical path through the water. There are 4 or 5 terminals depending on how your gauge reads. I'm betting it empty and the gauges are giving false readings.

If you can't get the rinser working they do sell a wand you put down inside the toilet that has a sprayer on the end. It's a bit more intrusive and possibly messy but they work!