One problem related to air conditioner has been reported for the 2003 Mercedes Benz C Class. The most recently reported issues are listed below.
While driving with a/c set on "auto" the a/c system would suddenly turn off by itself and would turn of repeatedly when started again. During such episodes the a/c would act erratic with fans turning on and off at different outlets, cycles between heating and cooling, and makes hissing sounds. This would occur many times a day on a daily basis in summer weather (except when the car is taken to the dealer, it seems). It took about 2 years for the dealer to finally fix the problem since they could not avoid admitting its existence after I had video taped the malfunction and showed them the video. .