Inspect flow cell to ensure flow is adequate and present. Backwash pool if flow switch is not touching sensor (left hand side).
Check sensor calibration - if actual pH value varies > .1 we recommend to perform calibration. It is recommended to first reset factory defaults before proceeding with calibration.
Inspect sensor - pH sensor should have shiny tip, not cracked, corroded, dirty of missing. Clean if necessary by following sensor cleaning guidelines. Check sensor using distilled water or alternative source with varying pH. Reinstall sensor and wait 30 minutes before performing calibration. Re - inspect in 24hrs to ensure that sensor is properly tracking. After servicing probes if sensors are not tracking please report problem to manufacturer or warranty center for replacement