i'd say you are testing in wrong mode for starters
You are supposed to have DC voltage on cell, not AC.
It's impossible to have VAC if you are measuring VDC (and that's probably why you are seeing such small reading).
Also in most modern SWGs you would see higher voltage and lower current when the cell starts to wear out.
In your case, i'd say when you measure using DC setting on your multimeter you will see 0 volts because your unit is not outputting anything.
That small VAC reading is probably just the noise on cables which can come from any source.
The test for the cell would be: give it the operating DC voltage from any source and see if it draws any current (makes sure your power supply and cable you use to connect the cell to it can handle 25 amps though). If you have 2 old but still working car batteries, that will do (you'd need to connect them in sequence and make sure the polarity is right).
Easier alternative: find someone with same SWG and put your cell on their unit and vice versa
There should be no continuity between silver and black plates, but depending on the cell design there might be continuity between same colored plates.
By the sounds of it it looks like your unit is just off/wound down to 0%, although you might want to confirm that with someone who knows more about Jandy SWGs.
I'd get someone who is qualified electrician to open the unit up and measure the voltages inside it to see where the juice stops flowing.
Obvious question: being 18 months old, isn't it still covered by warranty?
