I just acquired a used HotSpring Classic Model F manufactured approximately 1998. It has the following ozone generator in it:

Watkins Freshwater II Ozone Generator
OUA-283416

What is the lifespan of this model?
How can I tell whether it is functioning properly?
Does anyone have the owners manual and/or technical documentation on this model?

Replace it.

They get old like the rest of us - then they die.

That thing's almost 10 years old, time for a new one. One hose connection and a 3 wire patch to a plug. Takes less than 30 minutes.

Anything will work there... cheaper is better imo.

When I purchase a replacement Ozone Generator is there anything in particular that I should look for?
Any brand or model preferences?