What just happened ? Belt squeal and charging full?

Took the 70' Dart to the auto parts store for a new battery. The old battery was just getting weak and it was 8 years old. Ok, no problem. Drove it to the auto parts store. Got the battery in and drove it home. I was almost home and heard the belt squeal like something was locked up. I looked down and saw it charging like a mother. I almost shut the car off, but the squeal stopped and it came back to normal or slight charging. That alternator isn't more than a year old and probably only 2 hours of time on it. What the heck happened? Why did the alternator "brake" and then free up? Voltage reg issue? A few years ago coming home the headlights got super bright for a second or two. I was almost in the driveway then too. I think I changed the regulator after that. What just happened ? Thanks.

check where the regulator is mounted
maybe unbolt it and clean the area where it mounts, > has a good ground

I hope you didn't cause a short somewhere.......

As above check VR wiring and ground.

It might just be "coincidence" that something happened. Maybe the brushes are sticky, worn, and it wasn't charging for a few minutes, "you didn't notice that". Very hard to say, unless you can catch it again.

If it happens again, I would unplug the VR and nurse it home. If you are not using the lights, and not starting the engine 'a bunch' then it should run a long long ways on "just the battery"

Bad regulator. Had on years ago that would occasionally go full output. Belt squeal would be the result of belt slipping due to full output (alternator harder to turn), not bad bearings.

Ok good to know thanks.