Yeah electrical stuff is real tricky. Can't really offer a warranty on that stuff and just have to try / see it work before you sell it. The craigslist motor i bought, the alternator went bad after a few months driving on it. I know OEM can last so the previous owner must have done something to it to make it not last. Reason i know is i have a OEM B18c alternator with about 300k on it. It still works and i am the second owner of that particular engine. It's really strange how the craigslist alternator crapped out on me, and it looked to be a OEM based on the markings. Either way i got a brand new Denso and the 300k one sits on a stand. OEM is good stuff.