yjchua

Hi,

Title says it all.

In where I live for the time being (Malaysia), pollution's a big problem and I'm used to having air recirculation enabled permanently in my older vehicles.

In my W205 C300 (with Thermotronic), every time I enable air recirculation, it would always deactivate itself halfway during my journey.

Is there any way to leave it permanently enabled (without it turning off by itself?), or better yet, have it enabled automatically whenever I start the car?

Thank you.

GerritKw

I guess that is a safety feature. When you are in the car with 5 adults an only use recirculation, the chance on a low oxygen level in the car is increasing.

yjchua

Yeah, to keep the pollution and emissions from other vehicles on the road out of my car.

Three quarters of my time is spent in heavy traffic.

ManiacGT

Sealing the interior permanently will result in low oxygen and you will feel sleepy or ultimately pass out so recirculating air is usually turned off after a period of time. It also seals in poor smelly air.

gfmohn

My owner's manual (print or COMAND, I forget which) says recirculation will deactivate after 10 minutes. It may be different in Malaysia. For the reasons other commenters have stated, defeating the deactivation (continuous recirculation) doesn't sound like a good idea. However, in the next few years, the auto pollution regulations will become so strict that that the exhaust from new vehicles will be cleaner than the air coming in. During air pollution alerts, radio and TV news will urge people to get in their vehicles and drive around. Then, all those vehicles will be cleaning the air of pollutants from other sources. Until then, all you can do is turn off the recirculation manually when you reach portions of your drive with less pollution (if there are any) and then turn it back on when the air gets bad (resetting the 10-minute clock).