My fresh and gray have always read correct on both of our trailers. The black never reads right, I did the geo method, I flush the tank and even had the Horst Miracle Probes on the Rockwood without much change... We just wait til the thing starts to "birp" to gauge the black.
I will agree, though, there is many better solutions to the tank sensors.. But that would be some extra coin and hurt the bottom line.
Pat, Jen & Heather... Oh yeah and our trained attack trailer cat, Cinnamon
2015 ChevyHD D-Max
2014 Greywolf 26DBH