Hi,
That wire only gets 12v when the key is in the start position. So what you found is normal. Have you checked the connection at the alternator? If you have and it's good, remove the alternator and have it bench tested at a parts store. Most will do it for free.
Again, since the fuse only blows when the alternator is connected, then it is most likely the alternator or the connector.
Let me know.
Joe
Friday, November 6th, 2020 AT 6:26 PM