I thought I'd share my discovery/solution. My Intex SWG (Mr. G) started flashing the low salt light. At first my test results agreed and I added the needed amount of salt. I sent the kids into play to "stir the tea" as we call it. The remainer of the week Mr. G continued with the low salt beeping. My test results indicated that I was fine - maybe a smidge towards the low end of the scale but nothing close to the beeping end of the scale.
I decided to give Mr.G a good cleaning thinking maybe some build up on the plates was causing the missleading reading. I pulled Mr. G from the filter and filled the tube with vinegar. I let him soak all day. I did notice some buildup so I crossed my fingers. At 10 pm in semi-darkness (yes I'd forgotten about him) I hosed out the vinegar and reattached everything and started the system back up No code!
So if your SWG is throwing a low salt and you know your salt level is fine....it may be time to give your SWG a good vinegar soak.