Q: The AC smells like fertilizer.

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Hello, and thanks for your help. I recently bought a 2014 Mercedes C250 with 21,500 miles on it-and everything works well, except the air conditioning smells like fertilizer for the first minute or so after I turn it on. I am in Texas, and it is really hot down here, so the problem is exacerbated. Should I replace the cabin air filter? Is there mold growing in the ventilation ducts? Did something die up there? What should I do? Again, thank you!

My car has 21500 miles.
My car has an automatic transmission.

It sounds like you have mold or mildew in the system. The most likely place for it to grow is on the evaporator itself. That component gets very cold and humidity forms condensation on it. That moisture along with heat can foster mold growth. I suggest changing the cabin air filter and having the AC evaporator cleaned. There are products available that are made to clean the unit without removing components. It comes in a spray form and creates an expanding foam that disinfects and cleans your vent tubes and evaporator. Check your local parts store for the cleaner or have a certified technician, like one from YourMechanic.com, complete the cleaning for you. Afterwards I suggest running the AC on maximum, and recirculate to remove most of the moisture from the interior of the vehicle.

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