Add salt light stays on

[Alpi]

I have a salt water chlorinator and the "add salt" stays on continuously.

1. I have added salt and tests indicate there is plenty of salt
2. I have had the cell cleaned
3. There is plenty of chlorine in the pool and can 'superchlorinate' if I wish to

The manual states the cell might require replacing but as the chlorinator is still producing lots of chlorine I am not convinced this is the problem.

Could it be the circuit board or a faulty light or something.

Al