There are about six "dimples" around the top cover that allows it to "snap" in place. I used the end of a wide blade at 90 deg. under the lip and twisted as I worked around to "pry" at or near each dimple. Clean any dirt or loose rust off the top of the sender, so as not to get dirt inside when the cover comes off. These pics are what you will find inside. If it is not working, the likely cause is dirty contacts. I had to replace the arm that holds the float on my sender.