Air conditioning on 2005 Ford Expedition

Usually when I turn my A/C on I her the clutch kick on. Now I turn on my A/C and hear nothing and it blows hot air. How can I troubleshoot this problem?

Some main reasons the compressor will not activate:
1) refrigerant pressures too low - due to low refrigerant level (leak?)
2) compressor coil or clutch worn out or inoperative
3) A/C cycle switch failure

I would start by having the system pressure checked. Good luck.
What are the Fuses I should check on my 05 Ford EXBD.
A/C Not working!