GMC Repair: Air Conditioner Smell, gmc yukon, 2003 gmc yukon

Question
I have a 2003 GMC Yukon and have noticed a sour smell emitting from the air conditioner vents when I turn on the air conditioner. I have replaced the air filter and flushed the radiator. Is there anything else that I can do to relieve this problem?

Answer
check to make sure the A/C drain is free an clear, if not water is not draining and causing that smell, once you remove the water you can spray a lysol type conditioning with the A/C on recirculation, through the defrost, it will suck it through the system and coat the coils in the EVAP, check with your local parts store for a deordorizer for the A/C system.  Make sure all the water is out of the case, if its not the smell will return soon