Thanks guys. So many good ideas. The idea of the water causing the problem may be my problem. We stayed 5 months In Las Vegas and there isn't harder water anywhere. (That is where the sensors started acting up) I fought hard water stains everywhere. I bet the tank walls (that is why the full still works) have hard water build up. We dump every 2 days, can go 3 with normal use so it isn't crucial to have the sensors work, but I just like to have everything working.
I am definitely going to try the vinegar. That should help the hard water build up.
Thanks a million. I also had no idea that Winnebago put the sensors on the outside so since we keep our tanks clean all the time it has to be hard water sitting in there.