Hyundai Repair: musty odor w/air on, sonata 4, ventilation system

Question
2006 Sonata 4 cyl. 26,000 miles. When we turn on our AC we get a musty odor. We have taken the car to the garage and they have performed a AC maintenance on it where the supposedly "foamed" the coil. They also changed the cabin filter. The smell improved but did not go away. I took it back again and the mechanic showed me to spray Lysol spray into the air intake of the AC with the AC running full blast and the car doors open to exhaust the material being sprayed in. This does appear to help. Is this common among Hyundai? I have a 2004 Santa Fe which does not have this problem. My wife is very allergic and has asthma very bad. I am considering the need to trade this car.

Answer
The problem you describe is common on most types of vehicles, not just Hyundais.  The reason it exists is that the air conditioning system removes water from the air and some of this water rests in the ventilation system.  Lysol is a good product to use to try to eliminate the problem because it will help kill anything that may be growing from the moisture.  The only other option would be to remove and disassemble the heater-A/C box and clean it out entirely, but that may be cost prohibitive.