Let me start with this. I own a PA-28-140, in which a few weeks ago I replaced the alternator since it went bad. After the replacement, everything was fine until I got a report from the flight school that the aircraft is making a whining noise (high pitch) during flight. This has happened twice already. My first thought was like it was missing the alternator filter (which by the way I did not installed or transferred from the one I removed) because that it the sound you hear on those cars from the 70s & 80s before perfection came about. I have attached the YouTube Video here since I cannot upload the video in this forum. Any thoughts?
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