2000 ML320 - Musty smell coming from A/C-Heat when on. Is there a way to eliminate or does this indicate an issue that requires repair?

 

2 things...
1) in the passenger side footwell under the glove compartment, is the cabin air filter. Replace it. IF the smell is still there..
2) With the a/c controls set to a/c, but NOT on recirculation mode, and fan on high, take Lysol disinfectant spray and spray it into the ventilation intake at the base of the windshield underneath the wiper arms.

 

evaporator core should be cleaned. try Frigi-Clean and Frigi-Fresh. It's a notable occurance with Mercedes and other newer car manufacturers.

www.ac-evaporator-cleaner.com is where i got mine.