Air Recirculation Mode
WARNING: This page is about a different car, the 2000 Mercedes-Benz C43, 2000 Mercedes-Benz C280, 1999 Mercedes-Benz C43, and 1999 Mercedes-Benz C280. However, it is still accessible from the selected car via links, so may be relevant.
Pressing air recirculation switch causes air to be recirculated without additional fresh air. Air recirculation mode switch automatically shuts off after specified period of time. Air recirculation mode cannot be turned on if defrost button is pressed.