Had trouble with mine a few years ago. Found out where the transducer was and looked it over and removed transducer from cup. Did not know how they operated also and thought why is this thing sitting in a sealed cuplike closure.
So I added some river water to it and it worked fine.

Maybe save your $$$$ and just add some water when needed........................

I would use water for a quick fix but not long term because it will freeze and bust the cup over the winter, unless you think to empty it every fall.