Too many volts are being made after I installed a new alternator

About three months ago if that I replaced my alternator in my car listed above (Quattro), it fixed my problem or so I thought. About two weeks ago I noticed my voltage gauge was just over 15 volts. Then less than twenty four hours later my lights started pulsating (all of my lights ). Then the alternator sounded like the bearing took went bad. It sounded horrible. I turned it off immediately and parked it. I since have removed the alternator went to go get it tested and they said it was inconclusive at which point I realized I needed to ask a professional exactly what I could be working with here. I also was hoping someone could tell me the size of the alternator pulley that comes with my car.