My air handler unit inside works, but the outside unit only makes a humming noise and the fan doesn't turn. I can turn the fan by hand so I don't think it seized up. Any thoughts on what's wrong?

my air handler unit inside works, but the outside unit only makes a humming noise and the fan doesn't turn. I can turn the fan by hand so I don't think it siezed up. Any thoughts on what's wrong?

I'll answer my own question. It was the capacitor, $50.00 at the appliance parts store, 10 minutes for me to install it = cool house again.