Both the grey and black tank sensors went bad, corrosion in the phone connector sockets, and the open end was full of gooey junk. Looked like rubber cement inside. Looking at the new sensors [pricey little boogers] it was probably the clear diaphragm that disintigrated. Anyway, when I followed the calibration procedure in the manual for an empty tank and then poured 15 gallons into the grey tank,it reads 1 gal and 2%??? Any suggestions? I was thinking about sending the tank module to Visone RV to see if they would test it on their system. Thanks, Don Colapietro '06 Monterey LagunaIII donjanec@comcast.net