do you really have to replace that rear AC filter.....I pulled mine out the other day and cleaned it with compressed air, shook it, etc. Looked fine to me after 65k miles of probably minimal use.

 

I replaced it when I purchased the car. It's as clean as a whistle 25k miles later. I don't use the rear AC a lot myself. Funny you mention cleaning the filter. When I was looking in the manual on how to configure the smart key configuration it was talking about the rear door sill filters and said not to clean or wash them as this could somehow damage the rear AC system. Not sure how that would do it.

 

I changed mine couple months ago and now I have a wind/humming sound coming from the glove box

 

Was there a small gap between the disposable filter and the sides of the filter cartridge?

 

I just replaced my cabin filter last week. As I mentioned before, I get mine from Amazon. OEM Desno shipped to the house for cheap. Both the cabin and engine filter for like $38.

Anyway, looking at the filter you can see that the heavier coated side is facing down. This make sense as debris collects on the top of the filter and you would not want this blocking the charcoal coating. I don't think it makes a lot of difference but if you go with an aftermarket charcoal filter have the coated side facing down towards the floor. Also, a good comment about making sure that filter fits snugly into the tray so as to prevent air from going around the sides or vibration issues.

 

What draws the air across the filter? Is it some induction from the bottom of the filter? Or is it just the (forced) airflow that goes into the car (intake right below the windshield wipers) as the car moves forward?

 

Vacuum or suction from the fan motor located just below the filter.