mike, have you used the diagnostic button? push #5 should show you instant salinity - the unit has to be generating for a number to show. If you get ~ -3000 on the instant you can slave that number to the main display by turning the switch to SUPER and back to AUTO.

when you push the little black "diagnostic" button next to the display - it will show you (by push #):
1. Water temp
2. Cell voltage
3. Cell current
4. Desired % output
5. Instant salinity (with a "-" sign) (salt ppm)
6. Which unit you have
7. Which software revision yours has.
The units are supposed (!) to show 2600 as default - but I've seen some that show 1600 (the same reading you're getting... hmmm?). Try the diagnostic tonight, it may save you a $ervice call - we know that something happened to the computer, this may be a little one time side effect (another sign that the 1600 isn't a 'true' reading is that you say that the unit 'appears to be working'- if the unit actually thought that the salt was 1600, the low salt light would be on and the unit wouldn't generate)