looking at the service manual i don't see the rectifier / regulator location or it described in the schematic. Is it the CDI box and is it under the fuel tank by the ECU

 

You had one of the early ecm modules that controlled the fan,charging,etc. Look here on your model under "electrical" .Browse Wasn't under the general recall of ecm modules that I'm aware of,but it's still Chinese! Can't remember If I replaced any or not? Huge ATV Recall by Polaris - Sportsman and Scrambler OPT

 

OPT, thank you for the info, are there any tests that can be done?

 

The only test on the module was with a tester that Polaris sent when we had the recalls,BUT they wanted it back. Worked in the same way a battery load tester works,it put a load on the ecm and showed if it was good or bad. If you're not charging 14-14.5 volts back to the battery, the ecm module needs to be replaced as this was one of it's primary functions. Plus if you're not sure about the battery,just have it load tested at any auto store. OPT

 

I am sure the battery is toast, but i do have a load tester and will confirm that it is bad. them with a known good battery I'll see what the voltage at the battery is while running, before jumping into just throwing parts at it.
OPT, thanks for the help and info.