confusing readings on 4 year old SWCG

[alisonquilts]

[ Pooldoc note: the TLDR; for this thread is simple: most 4 year old SWCGs are, like this one, at the end of their lives!]

Hi y'all

We've never had any issues with our AquaRite SWCG since it was installed, other than a creature gnawing through its power cord. This summer we keep getting "low salt" readings despite the fact that we have had little rain, and so it seems like the salt concentration should be going up rather than down. When we add salt the warning goes off, and the readout goes up to a reasonable number.

Today, in addition to a low salt light I got a "check cell" light. Even though it is not time yet to check the cell I did, and it seems fine. After I put it all back together again it was working...and then it wasn't.

My questions are:

Can something make salt levels drop other than dilution and splash out?
What does a SWCG that is going bad (like maybe a cell wearing out?) look like? Do you get a whole range of weird warnings? Does the salt level read wrong? How can I independently check the salt level?

Thanks for any help!