Originally Posted by squidface
Now my alternator won't spin. I can spin by hand but when I turn it over it locks up.
That's strange. It's an alternator - its resistance to rotation is proportional to the power it is generating. If the voltage is fixed, the higher the current load on the alternator, the higher the rotational resistance.
I'm not sure what "locked up" means. If the alternator resists rotation in certain modes of operation, it is by definition working. Make sure to have your alternator tested
before you decide to replace it. Any Autozone or Advance Auto Parts will do this for you.
Right now you may be thinking everything is broken on your vehicle, but don't let that internal bias color your diagnosis.
Another thing to consider:
Why did your fan belt break? Perhaps you think it broke with age. Perhaps it's because the vehicle is old. But there's another possibility: If the alternator is shorted out, then its resistance to rotation is theoretically infinite. This could easily cause the alternator belt to snap without warning.