[buzzcop63]

We have different trailer but when I needed to Winterize I needed to work with the pump, called our local dealer and was told to listen to the sound! I think you have found yours, mine I had to feel in the carpeting covering the box that housed the pump to find two screws and remove them and lift up the covering board or in your case step. The screws are flush mount so they are hard to find if the step is carpeted. Good hunting!