Blackwater sensor problems

[dflickinger]

Here is my strange tale.

After dumping my blackwater tank, I started to fill the tank with water through the supply connection (with the blackwater tank valve closed).
I forgot (that day), that I was filling the tank and suddenly my wife and I heard and felt a "Thunk" sound. I ran to the tank and cut off the water then went to the toilet and found it half full of sewage. I checked everything and all seemed well, no leaks and everything working (and is still working), as it should, (lucky I guess).

Then someting strange started happening....I noticed that when I emptied the BT (blackwater tank) and then flushed the tank, the sensor lights would go down to empty as expected, BUT.... within 24 hours the sensors would read FULL again. I would go out and open the BT valve but I am sure that I would not get a full tanks worth of fluid from the tank. Everytime I empty the tank and flushed, the sensors react as they should (red to yellow to green to green) but again, within 24 hours it would be green to green to yellow to red.

Has anybody ever heard of this! Could something be filling the BT tank with water? Can the sensors really respond like this. The Sensors are reading correctly on the way down, just not (I hope), on the way up.

Let me know if anyone has ever had this problem

Thanks

["007"]

You say when you empty the tank on false indication you do not get as much water for a full tank.
The sensor may have some paper stuck to it and as water enters tank this paper gets wet to set off the sensor.
I'd get some tank cleaner when your tank gets near full and dump in and drive the coach over a wash board road to swish the water around tank and see if you can dislodge that way.
You can check level of tank by looking down toilet bowl opening, thats if it a straight short into tank.
The tank cleaner inlet if you have one may not be spraying the sensor in that area of tank.
The thunk you heard was the tank sidewalls expanding from water pressure, you may have had a RV movie experience if it went up the vent tube.