Low salt light "ON" on my Pentair SWG

I have the Pentair IntelliChlor SWG. The unit has been in use about 2 months now (although I bought it before my pool was dug so it is technically out of warranty). It worked fine for two months, recently the "add salt" light has been coming on. This means the chlorine will be produced at a lower rate until salt is added to the pool. The light comes on when salt level is below 2900ppm. The problem is my salt is actually at 3400ppm. I cleaned the unit (although no visible signs of scale) but the light remains on. Any idea whether this unit has a calibration mode? What should I check next?
Thanks

I have attached the calibration instruction so you can have the unit running correctly.

Thanks for responding. I got a copy of the calibration instructions directly from Pentair (e-mailed to me) a few weeks ago. The calibration solved the problem.
It's good to have a Pentair rep on the forum. I have a few other Pentair questions you may be able to help with. I'll post them as a new Posting.
Mike