https://www.roseummaple.com/2021/02/...um-system.html

That common blue wire should be unaffected by a freeze. It's just what is used to determine fluid level in conjunction with other 2 probes using resistivity/conductivity of the fluid.

Only downside, those DONT work on permeate (no minerals or compounds so NO conductivity). You would have to use float (mechanical or sensor/signal) for that application. I use that to shut off RO automatically on rinse/flush cycle.