black water sensor reads 3/8th all the time

[javamaude]

Please help, 2008 International 23', yes it's under warranty but my local dealer won't service it because I didn't by this one (it was used and he didn't have one) from him (this is my second bought my first Bambi from him) the other dealer is 100+ miles away.

So, I'm going to try to fix this myself. Tried flushing a few times, ice and driving, fill and treat with chemicals nothing worked. Grey water and fresh work fine. There has been some talk about wiring and checking the sensor. Anyone actually done this? Calibrating, can you mess the other sensors up?

Any suggestions would be great, and yes I am trying to contact Airstream about our crappy local dealer.