Any update on this? Also, have tried reading out the internal temperature of your IC40 with its "testmode" feature? You can find the procedure here:
Pentair Intellichlor ICXX SWG - Further Reading
I'm having the same issue. Mine is showing a salt level of 5500 in IntelliCenter. However, I have measured 3600 with the TF Pro Salt kit, and 3100 with a friend's digital salt tester.
This is my first full season with the pool, and I just added salt back in April. From the beginning, my cell would read around 4400 with a true salt level of 3600 as measured by both myself and the pool store. At that time, my water temperature was 70 F.
I read that the IC40 does not compensate for temperature. So, my guess is it has always had this problem, but now that the water temperature is higher (currently 85), it has pushed the salt reading above the limit, causing my high salt light to flash.
I've read a bunch of posts on here regarding high salt reading with correct salt levels, but none seem to post back what they did to fix it, or they just lived with it.
I did do the test mode on the IC40 last week to see if it was reading temperature correctly, and it was properly lighting up 80% with a water temperature of 84. Also, the IntelliCenter app is currently showing 85 in the Chemistry area. Not sure if that is the IntelliCenter water temperature probe reading or the reading of the thermister in the IC40 itself.
Today, I cleaned the cell hoping that would fix it. I inspected the cell, and it looked clean. I bought the cap to do the MA cleaning procedure, so decided to try that anyways. I added a 1:1 solution and saw no bubbles (expected, as it looked clean). Left it for 10 minutes, then flushed it out and put it back into service. It still read 5500.
Not sure what else to try. Sounds like if I call Pentair, they're just going to recommend a new flow switch. However, if it is showing the correct temperature, and good flow, not sure how that could be it.
Moved from here.