Hello, I live in Sweden and own a Monte carlo from 1974.
I thought I could get some help here from you guys.

My alternators bearings was going bad so I bought a new alternator.

It is basically identical to the old one, with the only difference being the markings on the connector.
The old one says "F F", but the new one has the markings "R F" above the connector.

Anyways I plugged the new one in, it charged normally and I took it for a ride. Then after a while it started to smell a bit burnt from the alternator, though nothing looked wrong.
So I drove home, then the alternator lamp in the dashboard lights up.
When testing the new alternator at home it didn't work anymore.
When plugging in the old one with bad bearings everything worked fine.

Did I do something wrong (thinking of the connector markings)
Or was the new alternator just bad from factory?

 

sounds like you did something wrong. should have just bought a bearing for the old one.

 

Then what are your thoughts about it?

 

without seeing and comparing partnumbers and Images can't tell you what went wrong. If the new one worked and then died something caused it to go bad. If the old one has only bad bearings but works, I'd replace the bearings.

 

I understand, I returned it to the store.
I worked well After I had installed it, and it charged properly. So initially it worked...
Driving on the highway caused the burning smell. As if it broke when it spun fast..