The problem is a poor design of the interior air handling system. There are two radiator like (heat/cooling) exchangers which live in a totally inaccessible assembly in the middle of the dash. Tight against the firewall. They become contaminated with mildew and or mold. That is the smell, and it can be embarrassing unpleasant not just to the owners, but their unsuspecting passengers as well.
First the good news. It can be sanitized which completely removes the problem. COMPLETELY!
The bad news. I had to do it myself. As far as I know, the dealer has not been given any guidance on the issue.
How is it corrected?
With several cans of "AC odor eliminator". I purchased mine from Napa .
https://www.napaonline.com/en/p/BK_7653141 Cost is $10.99 each as of this posting. I used 3 cans (they're not very big)
The product kills the organisms and it doesn't require rinsing as most household mold/mildew cleaners do.
The first can I injected alongside the air conditioner evaporator coil. To access that coil. I had to remove the glove compartment assembly. They using a dremel tool, I made a dime size hole at a calculated point in the "Air handler assembly" I mentioned at the start of the post. That allowed me to snake the long tube that comes with the product, right up next to the evaporator coil. I discharged the whole can. The foam gets into all the nooks and cranny's of the coil and its surrounding housing. I waited for the foam to totally liquefy and run off down the drain in the assembly which is for condensate run off. I then put a small piece of heavy tape over the hole, and reassembled the glove box. All this was step 1. It removed about 70% of the odor.
Step 2 was to do the same to the heater coil. Don't ask me why moisture loving mildew and mold get on a dry heater coil, but in this this design...it does.
Anyway, this part is much easier. There is a "drain" located under the car, passengers side. It is where the evaporator coil drain and heater drain discharge. They connect together under the dash board and exit as one hose under the car.
All you need to do here is snake the long lose that comes with the product, up as far as you can. Then pinch the drain hose tight against the product hose so the foam can only go in one direction. Up into the coil area.
I injected 2 cans in this area.
Because of the way the hose splits, very little will go toward the air conditioner evaporator. That why I did that coil separately. (90%) will go to the heater coil and the housing around it.
I waited several hours, then ran the fan on max to move any remaining product through the duct work.
It's been several months and the smell is still completely gone.
Since I wasn't sure it would work, I didn't take photos. But if there is enough interest, I would take the glove box apart again to show everyone where EXACTLY to drill the dime size hole. The drain under the car is easily visible, if you know where to look and what it looks like.
This wasn't a "cross your fingers" attempt.
I did a bunch of research on how Genesis designed the Air Handling System in this car. I found pictures of the assembly, and pictures of it parts/components. I was able to calculate precisely where these stinky coils where, and confirmed it by snaking a endoscope camera in where I had drilled my access hole. I could clearly see the air conditioner coil on my laptop. I taped the endoscope camera to the product injector hose, and guided it precisely where It needed to be. When I injected the foam product, I could see it on the Laptop screen via the endoscope camera. These USB endoscope cameras cost less than $20.00 on ebay.
