pool pilot dig220 warning "check/clean cell"


Nov 9, 2014
Albany, ny
This code has been flashing on/off since opening this year. Initially I was thinking that once water warmed up it would stop, but that hasn't happened yet. Water is 75, last week and was up to 79 before this last cool down. I added salt to get level to 3000ppm. The cell itself is crystal clear, no deposit buildup or anything, so I didn't soak in muriatic acid. Fortunately the water is crystal clear, have been checking Cl- levels every few days, and adding liquid as needed.
When I run test pool pilot here are the values.
Power level 2
18 volts, 4.0 amps
Cell SC 48
Salt 3000
Temp 75

The owners manual isn't really helpful, but the pool pilot troubleshooting (http://autopilot.com/wp-content/uploads/2016/10/error-code-digital.pdf) page indicates that this is low voltage and amperage, and would typically be a wiring problem-low incoming voltage. That seems odd since the set-up was here when I moved here 5 years ago and has always worked fine. I wouldn't be surprised if the cell is nearing end, or dead, but shouldn't that show higher voltage on the test?? Makes me think the unit is bad. I flipper breaker and that didn't change anything. Any suggestions for next step to determine if cell vs unit vs other? Thanks again!