During the A/C season we deal with smelly evaporators on a daily basis. MB has come up with several solutions in the past few years, but the only one that actually works is applying a dis-infectant, called Contra-Sept, (MB #A009 989 61 71) directly to the evaporator. I've used this treatment on pretty much the entire line of new MB's, but never on a W202. I'm sure it would work, though. Like Matt L says', the evaporator isn't easy to reach.

MB dealers have the factory supplied kit to perform this job. It consists of a pneumatic spray gun, and an application probe. We remove the evaporator temperature sensor and insert the probe to gain access to the evaporator core. One liter of dis-infectant usually does the job. We replace all the climate control filters before returning the vehicle to the client. The labor time is about 1.0-1.5 hours, depending on the vehicle.