My car smells like a compost heap when I open the air vents… help!
Sounds like Mildew may have grown in them. Has it been wet?
When’s the last time you changed the cabin filter, if equipped?
It might be compost. If leafy debris gets trapped in the cowl, or in the heater box, or plugs the drain from the AC housing, you’re on your way to a nice farmette. Mouse droppings can add local flavor.