I have just noticed when I start my car and my blower kicks in I smell a foul musty smell from the center air vents. This just started a week ago.
I checked the folowing:
Cabin filter is clean and does not smell.
Drain lines are clear in both filter box and A/C drain line is clear.
It seems to be more apperant with the A/C off. With the A/C on It goes away in a couple of minutes (probally due to dryer air) It makes no differance with recerc on or off.
Ran it with the filter off in the driveway, made no differance.
This is a very foul musty smell.
We have had a lot of rain with high humidity lately.
Could I have some sort of mold on the EVAP core or blower housing? If so what are my options? I'm not really keen on spraying something into the fresh air intake (air freshener) as I dont want the car to forever smell like fragrance and foul smell combined. I could just hang a fragrance tree from the rear mirror like an Escalade driver.HA HA (NOT AN OPTION!!)
It's really sad when we get in a car that is so beautyfull out side, sit down and still smell leather, start it and smell dirty diapers!!! How embarasing.
Any help out there?

 

If the evaporator drain is clear, dripping when on, look to make sure there are no leaves blocking the drains for the windshield. Especially on the passenger side.
I have another car that has plugged the two evaporator lines twice in 18 months. It is not moldy yet, just feels humid inside. Hope to have a chance this weekend to blow them clean.

 

what panelhead said. I've seen it on other cars. there are cleaners you can spray on the evaporator to get rid of the smell/mold/diapers if you have to, but getting a backed up/plugged drain is probably the first step.

 

My guess is you've ran with the A/C off for some time?
If so this gives the bacteria chance to build and grow, they love a warm moist, damp type environment.
I've experienced this really badly with a 2nd hand car bought years ago, really bad and could never get rid of it.

I'd certainly recommend doing all the checks as previously mentioned and also to buy an air con bomb

The aircon is put into its lowest setting at high speed with recirc on and the aircon bomb activated, it runs freely throughout the entire car and through the system killing any bacteria as it goes, they're pretty cool, I've used them several times to great effect