Hello John.There is a real simple Quick test.Ijust dont remember this minute.I am at work right now,when I get home I'll check myrecords.I called Mallory and they gave me the test or it was on their web site.It takes about a minute and a meter to tell,and it works.Mine was bad and Mallory told me to send it back to Summit and they sent me another one(it was less than a year old)Summit also sold me a unilite surge protecter for about 30.00.I beleive this a new part to help protect the module.The more I think about it I got the info from their web site.Hope this helps!FastE