but it shows empty before theres any use ? how long has this been going on ?
do you flush/rinse the tanks well after you dump them ?
I've seen cases where debris (think paper) gets hung up on the sensor inside the tank & gives false readings.
if the tank monitor reads full (when the tank is really empty/rinsed and clean) then you might have a wiring issue - the wires to the tank sensors are pretty delicate and theyre exposed to the elements - check the tank for wiring issues (you could have a wire broken or shorted).