Aircon stopped working

[leonb]

I drive a 2000 C280, and did not use the aircon for about 3 months (operate fans on EC). The reason for this is because it was winter time and I though I would save the aircon instead of kicking in/out all the time.

Yesterday I switched on the aircon for the first time (disengage EC switch), and it did not make the air cold. I can hear the "sound" change when engaging/disengaging the EC switch, as normal when it works. The fan still blows, but no could air.

Any suggestions on how to troubleshoot this problem?