Air Condition is not blowing cold air? on 2000 BMW 323Ci

Hi all, there is no difference in air tempeture when i switch on the air conditioning i have take out the pollen filter and it didnt seem to be that dirty....anybody have any ideas what might be the problem here? thanks

Asked by for the 2000 BMW 323Ci
Make sure the compressor is running
Check for fan operation
Check the refrigerant and see if the system needs to be re-charged