I have a 45K gallon vinyl liner pool with a Hayward SWP controller and t-15 cell. The salt reading would not show above 1700 even though when I had Leslie's test the water the reading showed 3K. After trying resetting the panel it would show -3200 for instant salinity for about 30 seconds then would go back to showing between 700-1700 and the lights went back on. I called Hayward and they said the cell was likely bad (even though I had the cell tested at Leslies and it passed and it is only 1.5 years old.) I bought a new cell ($600), hooked it up and turned it on and the exact same readings appeared. I recalibrated it again and nothing - both check salt and inspect cell lights came on and it did not generate chlorine. I called Hayward back and they told me it must be the PCB board. So I bought a new board ($200) and installed it about 7 pm last night. Added 80 lbs. of salt to bring my 3k to 3200 (just to be safe), turned on the cell and controller and it worked - salt registered at 3200 and it started generating chlorine. It appeared we had located and eliminated the problem. Checked it again at 7 am this morning and salt is reading at 0, and both lights are back on. Just for kicks I turned the power off to the unit for about 5 minutes and turned it back on. Salt still showed 0. I tried to recalibrate again. Put switch to super-chlorinate, instant salinity went to -3400 so returned the switch to auto. After 30 seconds salt reading came back at 1500 and lights went back on. I am now out $800, have 0 chlorine in my pool and the water is about 84 degrees.
Since I have now replaced both components in the system in the past 3 days and still nothing, anyone have any ideas? The system worked fine last year and this year (the pool has been open for about 2 months) until 3 weeks ago. This is now occupying all of my time which is exactly the opposite reason we have a SWG in the first place!