Tom in Austin

I wondered about that as well ... if the filters were installed with the arrows pointing in the wrong direction, would it reduce airflow or cause any other harm?

vudiff

In the first video in this thread (post #10), the YouTube comments section state "3) If you get filters that are directional (have arrows for airflow direction) make sure they point at each other (the service manual points this out and states it will cause damage if you don't, but I don't see any difference on the stock filters)."
In the second video (post #14) at the 1:52 mark, in the video she states the same as above, "make sure the air flow indicators point towards one another".

Also, if your statement was true "In the real world it won't actually matter anyway", why would MB & the cabin filter manufacturers specifically state which way to install the filters (air flow direction)?

Not trying to be a d**k. I'm just trying to have a conversation so we can all understand this, including myself. I've had numerous vehicles. Have always replaced the cabin filters as soon as I purchased vehicle & going forward once a year. The MB threw me off as the indicators are check marks, not arrows. Thanks to all for having this conversation as it's important, it's our health, because it's the air we breathe in a small space (your vehicle).

Tom in Austin

Oh good grief, outward, inwards, this is crazy. If it really makes a difference Mercedes should have designed the filters or the holder they go into so you couldn't install them the wrong way.

I'm going to call this poor engineering on the manufacturer's part. On Japanese cars most things are designed so you can't put them in the wrong way, or else it is very obvious how they go in.

zk2004mb

No this is WRONG. If you are looking for the answer like I did, here is my research.
https://www.youtube.com/watch?v=YQUi...yneA.Robertson Check out this guy changing his cabin air filter. Starting at 5:15 you can clearly see the dust accumulated at the side which is outside of the V shape, also can see the dust shows on the edge of the plastic panel rather than the center of the panel. At 6:22 you can see how clean the inside filter is. So the air is flowing from outside of the V shape towards the inside.
If you're still not sure about this, take off the panel, keep the filter in, turn on your AC, use a small piece of napkin paper, it will tells you the direction of the wind.

zk2004mb

This is also wrong. The direction of the air filter MATTERS. The size of the micro-hole on the filter is incremental from one side to another, so the larger particles get trapped first then the fine dust. If you use the wrong direction, the life expectancy of your filter could shorten.
A great demonstration: