I have had my '04 TL for about a year now. Has about 20k miles. There is this sour milk smell when the AC switches to fresh air. It stops when I change settings to recirculated air. Been noticing it for a few days and wondering if it is time to replace the internal filter. Anyone know what is going on?

 

Yep, could be the filter and some mold in the air passages. Dealers have some disinfectant that they can spray into the passages to combat this issue.

 

AAAAHHHHH! So, that's what that smell is! I use the recirculate function quite a bit and have been noticing that ever lingering odor (thought I dropped a milkshake in the back seat.....last year).

 

advice that i got from the forum is to turn off the climate control when you are like 5 minutes away from your destination. that way when you arrive there will be less likely the chance of condensation where mold can form. this is of course for the warm weather climates.