D,
Welcome to TFP... a great place to find the answers to all of your "Salty" questions...
If the salt reading on the ET, or ScreenLogic, is zero, than that normally means that the cell is not communicating with the ET. In a few case just turning the system off and disconnecting and reconnecting the cell connector and then turning the system back on has corrected the salt readings. It has happened to me..
If the cell really thinks the salt reading is zero, it will turn on the low salt light and the cell will not produce chlorine. If the problem is like most that have recently been reported, the cell seems to work fine, it just does not tell the ET, or ScreenLogic, the salt level.
If the system is under warranty, then you should call for warranty repair and let Pentair handle it..
If the cell is out of warranty and the cell works, other than reporting zero salt, the best approach is to just use it the way it is. As long as the low salt light is not on, the cell will produce chlorine, and knowing the salt level is not all that important. At least not important enough to buy a new cell.
You can try replacing the flow switch, which has a thermistor in it that is part of the salinity circuit.. But, generally the flow switch only causes the salt level to read low, or read high, in relation to the actual salt level. I am not sure how it would be possible for it to make the salt level read zero.
Thanks,
Jim R.