Just bought a house with a Pool Pilot DIG-220 system, and my chlorine is very low despite adequate salt levels so I looked at my control box. The display works but never changes from "Pool Pilot Digital V4.2" no matter which buttons I push, although certain button pushes will turn the display on and off. The box is obviously very old (plastic is flaky, all button labels are gone which you can see on the edge of the picture) although all the buttons still click. Any suggestions on what to do, besides adding liquid chlorine temporarily? Pretty sure this box is no longer under warranty.