get the system re gassed and get dye put into the system to show if any leaks are present....if the aircon is working, with the car idling when you switch the air con on and off you will hear the aircon compressor click in and out.
use the aircon once a week winter and summer as then the gas circulates and the oil suspended in the gas gets to lubricate all the internal seals.
ray
July 2011