I have in fact removed the sender and tested resistance with a multimeter -slid the float up and down the shaft, observed the change in current as consistent with what I’ve read to be “full” ”halfway” and “empty.” There was no sludge or crud on the wires either. I’ve never had any issues with fungus in my tank. I was almost a little disappointed after pulling the tank screen only to find it perfectly clean!

__________________
1981 240D 4sp manual. Ivory White.