How can too much salt affect SWGs?

[dbooksta]

I can understand how too little salt could be a problem, but how can too much salt interfere with the operation of a SWG?

I have a Hayward Aqua-Rite and its manual seems very emphatic that it not be run with "high salt."

 

[JasonLion]

High salt decreases the electrical resistance, which increases the current flowing between the cell plates. Most SWGs are designed to only handle salt/current up to a certain level, and if current/salt gets too far above that the power supply will burn out. The AquaRite, like many other brands, will shut it's self off before anything breaks/burns out.