Musty odor when in recirculation mode.

 

Have you checked and replaced the cabin air filter?

 

You may also need to clean out the A/C system. It is not difficult. Get one of the many A/C foaming cleaning kits that you spray thru the vents etc. Available at AutoZone, Amazon etc. Be sure to remove the cabin filter before using one, otherwise you end up soaking the filter with the cleaner, which also prevents it from reaching part of the system. I like this one http://www.autogeek.net/1z-einszett-...freshener.html

 

Musty odor when in recirculation mode.

 

Then follow the recommendations in the above posts and it should go away.
When changing the cabin air filter make sure the system is in recirculation mode as that is what the owners manual advises. There are many youtube videos that show how to do it. You get to it thru the glove box. It takes 5 minutes.

 

There is filter with activated charcoal. There is an uncharge for this type of filter but it can address the smell. The activated charcoal looses its effectiveness over time.

Running the heater and parking in the sun can also help.

Salim

 

I used one of the spray kits available at my Toyota dealer. Worked OK.

Once the smell is gone, it WILL come back if you do not shut off the AC a couple of miles before your destination. This allows the built-up condensation in the AC system to evaporate so it won't get moldy. It is necessary to shut off the AC in more humid environments.

 

You can always try spraying Lysol through the vents below the windshield until it comes out the interior vents, then shut the car off for 30 minutes to let it dry and kill mold. Always remove the cabin filter first!
That is how my local Honda dealer handled this issue back in the 90s before there were kits for such issues.