Tank indication mystery

[JeffD]

I checked my tank levels the other evening and noticed that my black tank had 4 lights (Full) and my gray tank had 3 lights. I knew this could not be correct since I had just dumped earlier that day and both tanks indicated empty. Did some research and determined that the readings had to be false. Later the next day, I checked and both tanks indicated empty - one light on each. Later that night, I checked them again and they indicated full again.
After several days, I have learned that when I check the levels during the evening, they indicate full or almost full, but during the day, they indicate what I would expect. My only explanation is during the evening, condensation forms on the walls of the tank and triggers the sensors to indicate. Temps during the day are hovering around 90 degrees and about 60 at night.
Anyone else notice this? Is my hypothesis correct or is there some other explanation for this phenomenon?

[us71na]

This is a very common problem. The factory supplied level indicators are overly sensitive to moisture and give erroneous readings most of the time. In the black and gray tanks any bit of debris will trigger the sensors. Washing the tanks helps, but the problem comes back on every fill up even with the calgon and other treatments.

There are after market sensors that cost considerably more than the factory ones that are supposed to be better, but I have no experience with them.