Turn an alternator by hand?

[Feek]

Simple question, should I be able to turn an alternator by hand?

Long reason for asking - I've got a problem with the Feekmobile which KwikFit told me is down to the alternator, they put their tool thingie on the car and it appears that it's overcharging. The result is that the battery light is on all the time and I notice the lights getting brighter and dimmer. I can even tell this from the interior light or the battery light on the dash.

A couple of years ago I had electrical problems with turned out not to be the alternator but it was replaced anyway. I had the old one which was taken off the car tested and it was good.

So today I grabbed the old one out of the outhouse, doesn't get damp or too cold) and tried to turn it by hand, but I can't. Does this mean it's seized or should I not expect to manually crank it around?