Hey Brian, one of my buddies had the same problem last year on his Polaris sled. In general the only way to really test a CDI box is replace it with another known working unit for the same make model year. Although we never really investigating what other issues could be cause the CDI failure. So basically, if you confirm your CDI box is failing, you really need to replace it regardless. We actually found a company located in New Hampshire, who manufacturers a Polaris CDI
as well as other electrical parts for snowmobiles. Maybe you can reach out to them since your in NH. Hope this helps. Happy new year!