I am having the same problem. Pool Clown helped me before so I am looking for help again. I have a Jandy Aquapure 1400 that is 6years old. It has the code 121 showing. We have cleaned the cell. How do we test it at the cell with the 3 posts. Is the middle neutral and the outside 2 for the positive? If we need a new cell, any recommendations. The service service light is not always on.