Thetford Tecma Head Tank Monitor

[dgrover]

My tank monitor has a green, yellow and red light on the display for empty, half and full tank indicator. This season it stays yellow unless we flush out the tank a couple of times after emptying it. It goes back to yellow much quicker than it should, and then to red much sooner than the tank is full. I also tried using the Thetford tank guage sensor cleaner in the tank with no success. Any suggestions would be appreciated.