What A81 Means
A81 means the turbidity sensor is still responding, but the value it returns sits outside the band the controller accepts. F&P's first instruction is to clean the optical lens down in the sump, then to check the harness, and only after that to consider a new sensor.
Common Causes of A81
- Grease or limescale film across the optical lens
- A harness connection degraded at the sensor
- A sensor that has drifted beyond its usable range
🔧 One Safe Check You Can Try
Take the filters out, then wipe the small glass window set into the sump floor with warm soapy water on a soft cloth. Baked-on grease there shifts the reading exactly the way this alert describes.
⚠ Why You Shouldn't Go Further Than That
- Cut power at the breaker and let the tub cool before reaching into the sump, since the heating circuit shares that space.
- Anything abrasive used on the lens leaves a haze that behaves like permanent soiling and cannot be polished back out.
- Out of range and completely failed are different states with different fixes, and the alert code is what separates them.
- Filters go back on a gasket with only one correct orientation; refitted the other way they let food debris straight past.
Opening a panel to inspect or repair something yourself doesn't automatically cancel your manufacturer's warranty — but it can risk accidental damage, and some manufacturers do have specific service conditions. Check your product's warranty terms, or ask us, before deciding.