2003 Mercedes C-Class Owner's Manual - Page 161

Controls in detail Automatic climate control* i If you keep button O pressed, the side windows and the sliding/pop-up roof* will be closed. The air recirculation mode is activated automatically: at high outside temperatures if the concentration of carbon monoxide and nitrogen oxide in the outside air increases, for example in a tunnel Please note that the charcoal filter must be activated (see below) for the air recirculation mode to be activated automatically. If you have turned off the air conditioning ( page 163) or the outside temperature is below 41°F (5°C), the air recirculation mode will not switch on automatically. Deactivating Press button O. The indicator lamp on the button goes out. At outside temperatures above 79°F (26°C) the system will not automatically switch back to outside air. A quantity of outside air is added after approximately 30 minutes. Charcoal filter An activated charcoal filter markedly reduces bad odors and removes pollutants from air entering the passenger compartment. Activating Press button e. The indicator lamp on the button lights up. The system switches automatically to the air recirculation mode if the carbon monoxide (CO) or nitrogen oxide (NOX) concentration of the outside air increases beyond a predetermined level. i If you keep button O pressed the side windows and the sliding/pop-up roof* will be returned to their previous position. The air recirculation mode is deactivated automatically: after five minutes if the outside temperature is below approximately 41°F (5°C) after five minutes if the air conditioning is turned off after 30 minutes if the outside temperature is above approximately 41°F (5°C) 161