I replaced the non-functioning level monitor system in my Coachmen with a
SeeLevel II system that uses external sensors. The sensors are relatively insensitive to tank crud, although a thick enough buildup can cause a misreading. The system reads the tank levels in percentages instead of the much less accurate "Empty, 1/3, 2/3, Full" system, with the battery level reading in volts of course. The installation is easy if the existing tank sensor area is fairly accessible. I used the 709-PH model that also has the water heater and water pump controls on the monitor panel.