Clearwater Zodiac LM3-24 will not SuperChlorinate

I am working on getting my mother-in-law's pool going this year. I wasn't covered last fall so I am working with nasty conditions. I had my water tested today and my salt is 3900 ppm (manufacturer suggests 4000). Earlier today I was able to put the generator on super chlorinate but after I back washed my filter this evening it would not go back to super chlorinate setting. I also cannot adjust the output levels. Does anyone have some suggestions for me?

I don't have that kind of SWG. However, you are proably better off just supercholrinating with bleach. I have the Polris AutoClear and they tell me that the unit is not intended to balance water. So, first balance with regular old chlorine, then when you got it right use the SWG.

Ill give it a try. Thanks for the help.