Low Salt Reading on Aqua-Rite When T-Cell-15 Passes Tests

[sfern]

First time poster, long time lurker. I am experiencing low salt readings on my Aqua-Rite SWG and the T-15 salt cell passes the Hayward cell test.

The system was installed in 2007. Over the years I have replaced the cell twice. In June, 2014 I replaced the current limiting diode (thanks to the TFP forum) and this fixed an incorrect salt reading. This spring the average salt reading dropped to 2600. The Taylor K1766 salt test result was 3000. The pool store salt test was 3100. Over the next several weeks the average salt reading on the Aqua-Rite has dropped to 2400.

I had the cell tested and it passed. I thought the problem might be the current limiting diode so I replaced it but the display was still 2400. I had the cell tested again at a different pool store and it passed again. I bought and installed a new main circuit board GLX-PCB-RITE. The salt display is still 2400.

I forced the average salt to 3000 by 1.) moving the switch from Auto to Off and back to Auto, 2.) setting the diagnostics display to instant salt, 3.) moving the switch to Super Chlorinate when the instant salt reading reached -3000 as it was moving down to -2500. Below is the diagnostic data after this process.
3000
89
26.7
6.29
30p
-2500
AL-0
r1.59
t-15

The cell will generate chlorine at this point. Inevitably the average salt slides down to 2400 and the Check Salt and Inspect Cell lights come on. I cleaned the cell 6 weeks ago.

It seems that my only option now is a new T-cell but it feels like an expensive guess when I’m not sure it will fix the problem. Can the cell pass the test but still be going bad? Should I use a cheaper generic cell since I’m really guessing at this point?

Thanks in advance!

 

[JamesW]

Probably a bad cell. How old is the cell?

 

[sfern]

Thanks for the quick reply. The cell was replaced in June, 2015. Should I ignore the "Passed" tests on the Hayward cell tester? Also, do you have an opinion on non-Hayward t-cells?

Thanks for all the valuable information on the Forum. You guys have saved me many times!!

 

[JamesW]

If you divide the instant salinity by the actual salinity, that gives you the performance of the cell.

75% and over is what I would consider to be acceptable.

Below 75% is what I would consider unacceptable and time to replace the cell.

You can probably get a little bit more time from the cell by increasing the salinity to 3,400 or changing the cell type to T-9.

As long as the average salinity stays above 2,400 ppm, the system will continue to produce chlorine.

I wouldn't have too much confidence in the store tests.

I would recommend the genuine Hayward cell.

 

[sfern]

OK, thanks again for the information.