Thanks for the info on the charcoal filter. Sounds like it's right where the W202 cabin air filter is. Fact is, I haven't turned it on (by the switch) more than a few times anyway. As to the A service, I don't know what this is. My car's system has never displayed anything but miles to "B" service. If it's just an oil change then I'm OK since it was done at about 4000 (replacement of oil level sensor) and again at 7200. Now 11500 with 2400 to go to "B". Oil, filter, and cabin air filter again, I guess.