JohnBoyToo

I had this on a previous car and it was condensation/ moisture in the lines/vent...
when it first came on it was the worst.

That would explain the smell mitigating when you turn on the ac... as the ac serves as a dehumidifier....

It can be fixed, just isolating where it is, and finding out how the moisture is getting in there and getting musty/moldy.... good luck

tommych

Thanks for sharing your experience, JohnBoy Too.
It sounds similar to the problem you had.

Did you actually have moisture leaking into your vents?
I live on the "wet" (west) coast, so there is a lot of rain that falls. Could it be when the fan vent is on, that "wet" air is being pulled through?

JohnBoyToo

I would challenge your definition of wet - it's all relative as I worked in Louisiana and the wet was from above and below !

Not sure of the source as I brought it to the dealer and they fixed it -
IIRC, when I asked, they either cleared a drain tube, or reran it as it was kinked -
think the high humidity there made it worse than it would have been...

good luck and if you park outside, have also heard that it could be animals making a home in the nice warm confines of your engine bay....

sakimano

you have to buy the cleaner, and do the full system clean. It's very DIYable...and the cleaner only costs about $20.

Or you could have the dealership do it for about $180.

rocco_ca

I went to my Audi dealer and they confirmed this bad smell from the air vents is completely normal if you don't use your A/C once in awhile during the winter months.

They have a treatment for 59.95$ that cleans out all build-up bacteria in the vents.

tommych

Thanks for all your suggestions. I think the smell is from the residual moisture after the a/c is turned off.

My mechanic did the a/c cleaning, but eventually the smell does come back. He said that some clients turn on the "heat" for a couple of minutes before they turn off the ignition to "dry out" the system.

DR. Q

I have the same problem.... I don't care but now that my wife is Prego she doesn't even drive the truck. apparently her sense of smell has heightened

tommych

I also have a 2002 Jetta and it never had this smell from the vents when the a/c is off.

Soni

my Q5 has the exact same problem....once I turn off the a/c, the smell will blow out immediately and my wife always ask if I just farted....
PS. she sits at the back seat along with my 16 months old son, so most of the time she doesn't see me switch the a/c off.

hollywud22

I'm sure glad I don't have this problem.....my AC just died.