Ac system.. Clutch?

[NC318e30]

Would like to get my ac working before it gets terribly hot. Car came without the belt there, so I got a new one and still nothing. With the belt on I do get squeaking and it appears when I push the button to turn the compressor on the compressor kicks on but it seams the clutch may be bad? The clutch looks to be spinning more slow than the rest and not fluently. Based on my sight glass I still have r-12 in the system. So my question is can I change the clutch without having to empty the system/take the compressor off?
Thanks

[MR 325]

You need to hook gauges up to the system to check the freon level. If it's too low the compressor is not going to engage.

[b*saint]

Yea its an electromagnetic clutch so you need to have your pressure switched in a changed state to make the clutch pull in. Also you can force 12v to make sure the clutch actually works. If its been sitting a while sometimes the clutches seize up. Mine worked but I had to take some shims out because it lost its oomph for closing.