Do you know of anyone else who is running a Humminbird DI model unit so that you could test your unit on their transducer? This would eliminate the unit as a possible cause of the problem you are seeing.

Hope they did not damage the DI transducer when they removed to reposition it… On inside-the-hull (bilge) mounted transducer you have to test them like Rickie stated (weighted down with water around them) to make sure that the location will work. Otherwise its just a guessing game.