Tecma toilets

[rusty]

My class c black tank has an attachment to wash out the tank that I use after every trip. We went to New Orleans and on to Tucson. It started in Louisiana that my Tecma maserator toilet started showing full tanks when they were less than a quarter. I washed it out a couple of times and got it to show green. But after 2 or 3 hours on the road it showed red. I looked but couldn't find a good product on the board to clean the tank just for odors.Could heat be a problem with the sensor? Has anybody had any experience with tecma?
Wayne