I recently moved to a new house with a pool. The pool is approximately 6 years old.

My Pure and Clear SWG is showing "Low Salt" via the idiot light. Here are the readings from the water tests:
TC= .5
FC= .2
CYA= 80
ph= 7.5
TA= 100
Salt= 4000
I added 4 bags of HTH Super and 300 lbs of salt when I opened the pool 2 weeks ago. I added one gallon of 5.25% bleach on Friday. That's it.

Obviously the light isn't working and from what I've read that could be caused by scale on the plates. This SWG is the old in-the-pool style and cannot be removed without pulling the wires through. When the unit is on, it puffs out a nice white cloud. Is this normal? Does that just mean that it is working?

I've called all over the place and found one place to get a replacement cell for this SWG. It will run me about $300. I called Polaris and they'll offer me one of their new Autoclear systems direct for a price that I don't really think is all that special. Should I buy the replacement cell or get a new complete system and apply the cell price to that?