We upgraded the stereo system in my car 2012 Mitsubishi Eclispe Spyder SE 2.4. We purchased a higher output alternator (supposed to be 200amp) but after installing it starts at 14v and then after idle for a few minutes drops well below 12v. DC amps 18.
I am assuming this place just sold me an expensive stock 100amp alternator with a smaller pulley on it. Because everything, but the pulley, is identical.

Question: I have been searching far and wide to find a high output alternator but have had no luck to find one that fits my car. Does anyone have any suggestions on websites to check? Or any suggestuons on what the hell I need to do? The alternator we purchased was $350 so I thought it would do what it was advertised 😕

Right now it is sitting with a brand new $380 battery in it that is only going to slowly die if I don't find something 😕