I had to change the AC Compressor on my 2008 Ford Focus. This video shows the process I went through. The AC compressor is the same on 2009, 2010, and 2011 models, too. I have a 2.0L SFI, 4cyl engine. To do this I had to remove the Power Steering Pump. I replaced the Serpentine Belt, Thermostat, and Lower Radiator Hose, too.

Checking AC Fuses and Relays:    • 2009 Ford Focus AC Relay, AC Fuse & C...  
Remove and replace Serpentine Belt:    • How to Replace a Serpentine Belt  
How to diagnose AC system:    • How to use AC Gauges in Your Car (AC ...  
Remove Power Steering bolt:    • Ford Quick Tips #75: CIII Power Stee...  
Recharge AC:    • How to Properly Recharge Your AC System