This kind of a product is generally the most effective:

DWD2 - Products

Some dealerships and mechanics have this product or something similar to it. I'm actually going to have it done to my car, which is about four years old now.

Reading on some forums a while back for a quick-fix, I did the Lysol thing, spraying it into the outside vents but also the inside ones. It works as a temporary solution, but that's all it is. In addition, spraying it doesn't go all the way through the system, plus eventually when spraying it into the vents, some of it touches the louvers in the vents and can build up.

There are a lot of good tips already mentioned, but personally in the last 30 seconds or so of driving after having the A/C on for a while, I'll turn it off and turn the fan strength up just to blow out the vents.

 

In Florida, we always run “max” air, which simply means that it recycles the inside air. It’s the only effective way to A/C a hot environment, and of course Florida is very humid. I’ve never had an issue with mildew or smelly condensers in any of my cars, including the Fit. If the Fit has a filter, then remove it and see if that provides access to the condenser. Most likely it does..it looks like a small radiator. Don't touch it or you could damage the fins. Get a small spray bottle and fill with distilled water and Pine-Sol. Spray the condenser getting it entirely soaked and ensuring that the fluid is flowing out below onto the driveway. Spray again, but with distilled water only. Flush it good. Install a new filter, since the original probably got wet and contains mold and mildew. Smell the old filter and see if that was the problem. Don't waste your time spraying the vents, thats not the source of the smell. Most likely you have a water drainage issue...maybe the filter got damp.

The outside vent (just in front of the windshield) allows both outside air and rain water into the vehicle. The rain water is intended to drain out...if there is any type of clog or issue, it could perhaps dampen the filter and cause an issue. When I changed the A/C filter in my sons Toyota last month, it had a few leaves and pine needles on the top side of it.

 

Ok, so this evening I sprayed some Lysol in the outside vent and ran the fan on fresh air half-way home. Then I pulled over, took out the glove compartment, sprayed some Lysol in the interior intake per Steve244's directions (thanks again), blasted it on recyled air the rest of the way home, and am now turning off the A/C prior to arriving at my destination. Mold smell is gone, and replaced with a pleasant clean smell. Score! I'll keep you all posted if/when the smell comes back.

 

cool. Get a cabin filter from Honda and pop it in. The old one will probably start to smell again. A clean filter will also increase cooling inside the car (increased airflow).

 

Can everyone just stop with the cabin filter as a culprit? It's not the cabin filter. Cabin filters don't really smell unless there's a ton of crap in them, and it's never mold in a cabin filter. Culprit is the crappy air condensor. No matter what I do this smell returns, yes i have it on fresh air. I've sprayed all kinds of cleaner. This is a design flaw and affects those in humid climates.

 

+1. There seems to be a design issue where it is worst in this car. Have you tried einszett 961105 Klima Cleaner Professional? I have heard good things and bought a bottle but have not applied it yet. Hoping for good and somewhat long term results.

 

last I checked it's the dead of winter in Wisconsin. Mold odors shouldn't be an issue. Maybe something crawled in there and set up housekeeping.

For the record, I've haven't had this issue since I lived in Florida, and then the fix was to leave it on fresh air, even when not in use so the coils could dry out. That was about 10 cars and 20 years ago. I haven't had this problem with the Fit over five years in the south...

 

I found Walmart version of Lysol to be more effective order cleaner.

 

I'd like to second this. My old honda civic never had the problem, or any other car I've had. I NEVER run on recirculate. I've replaced cabin filters, sprayed stuff down the vents, even run the 1Z Klima Cleaner product, and all of that only is a temporary fix, then back to the problem again.

I even tried turning off the AC the last couple minutes of a car ride and blasting the fan to knock water off the AC.

I'm very sensitive to mold/mildew, so this just freaking sucks. I'm about to take this car to a mechanic and see if they can open it up and operate, otherwise I'm out of options.

 

I've owned 5 cars in my lifetime. I've never once changed a cabin air filter. I just bought a 2009 Honda Fit Sport and never thought to change between the air settings when I was test driving it (just tested the A/C and Heat). Well the other day I changed it to fresh air to defrost the windows and noticed a horrid musty/moldy smell. I'll be changing the cabin air filter just in case but it definitely sounds like a design flaw. Especially with multiple people with the same complaint.

 

Someone posted in another thread, the filters are present on cars today not to protect your sense of smell or sensitivity to allergens, but to keep the evaporator from becoming clogged. This happens because the refrigerant used today is different from 15 years ago. The heat transfer properties of the newer refrigerant requires more fins, spaced closer together. This is the same as furnace filters: to keep buildup of dust on the inside of the furnace and A/C from being a problem. Sorry my google-fu is weak or I'd post a link.

This filter can become the source of some odor. I've noticed this in less than two years. It's due to the trapped organics (mostly pollen). Replacing the filter can result in fresher smelling air. I replace every year after pollen season. Please don't have the dealer do it for $80. It's a $25 filter online from Honda parts and takes less than 5 minutes without tools to replace.
Rodents have also been known to enter this area and poop. This is a design problem; there should be screens to prevent this.

The other reason to replace the filter is to increase airflow over the heating/cooling coils, increasing efficiency. The Fit's A/C needs all the help it can get.

Mildew can be a problem. If someone has left the fresh air setting on recirculate for long periods mildew can form. When the coils are warm and moist (after the car is turned off) it's an ideal media for growing stuff. Once established it can be hard to get rid of. This is true of every car made. I first noticed it in Miami on an '86 Toyota. I moved there from Utah where it was never a problem, but the increased humidity in FL and leaving it on recirculate prevented the coils from drying and allowed mildew to grow. Simply putting it on fresh air before I turned off the car and let it sit allowed enough drying to occur to solve the problem.

There is also another odor I've noticed when turning on the A/C when it's not very warm outside. I think the state change of water from vapor to liquid on the super-cold coils in these conditions releases an odor. I'd describe it as slightly acrid but not mildewy. This goes away after a few minutes of use. If you've ever snuffed the exposed cooling coils on an old style Frigidaire when the compressor has just started to run, you know what I'm talking about...