Thank you for the info. I will try this and get back to you. To answer the question though... When I plug in the aquatrol, it comes on, lights work, pump comes on, water flows through pool. But moving the switch from off to on or to timer or any position does not change anything. I cannot turn it off with the off switch, which is how I normally do it. I have to unplug it. I can use the diagnostics button, I shouldn't have said that exactly.... I just don't know if it is reading correctly; that's what I meant. Says my salt level is fine, but pool store said was low. Have added salt. My T5 salt cell looks clean. It is 7 years old. I cannot be sure that chlorine is being generated. It is VERY hot in Texas right now and I have turned up chlorine production knob; maybe just getting used quickly? I had a bit of algae growing and have been doing algae treatment followed by shock treatments (total of 3 times this week) My chlorine levels are good on test strips, but the free chlorine is low. CYA is low, need to go to pool store (will get there Tuesday) and all other tests are fine, pH etc. Water is now clear (basically by yesterday, Saturday, it started looking better and today Sunday it is clear.) Squirrels have been eating the pecans off the tree right over the pool this year, creating a large mess daily (and I clean it daily... at first I thought the green was from the green pecans (they are not the "real" pecans, I call them pre-pecans, they are green) staining the vinyl. Took me a minute (and the water getting darker green) to realize it was algae (I never had this problem until last year, so am a newbie at algae knowledge))I have never taken the panel apart, but I will do this and look for what you mentioned. Thank you!