Cabin air filter & air flow direction

Top to bottom; the proof is that the dirt and leaves accumulate on top of a used cabin air filter.

 

Great filter. I have been using it for sometime in my offroad vehicle as well. They filter so much netter than the OEM, and cost the same or less. You can also clean the filter with compressed air to extend the life for quite some time.


As others have said flow is top to bottom.

 

I have viewed several discussions on this question which way does the air flow in the Prius blower housing. I am now more confused than ever so that I will just have to evaluate my Prius. Arrow points up in the direction of the air flow. Others claim that debris is collecting on the top of the filter. Viewing my filter with what appears to be the dirty side is the top but the air flow directionds shows upwards. Answer to come later. Unfortunately who knows how many Prius configurations there are?

 

The arrows indicate the orientation of the filter for installation, not the direction of the airflow.

As stated above in several posts, airflows from top to bottom.

The filter is installed with the arrows pointing upwards.

 

The wrinkle in the original post was that some aftermarket filters are marked with an airflow direction arrow, in contrast to the Toyota filters, which are marked with an up arrow.

So the first thing anybody needs to figure out is, does this new filter I am looking at have an up arrow, or a flow arrow?

If it's an up arrow, install it pointing up. If it's a flow arrow, install it pointing down.

 

Is the only issue here, to ensure that after some use, the filter is not removed, and (inadvertantly) flipped over before reinstall?

If the filter appears to be symmetrical faced, I'd just mark the front edge with an arrow saying "this side up", or "this side down", and install that way. If the filter already says something like that, prominently, follow it.

Too, cabin filters didn't exist, a few decades back. I rank them with dryer sheets.

 

Ah, those were the days. Back when the autumn leaves would get finely mulched by the blower wheel and then packed tightly under air pressure between all the evaporator fins, which you'd have to take the dash apart to clean out.

I had an evaporator soaking for a few days once in a wastebasket filled with warm water and some of those digestive enzymes you buy to pour in a septic system. That turned all the packed leaf powder into glop, which could then be flushed out with the pressure wand at the car wash. A pretty successful operation, all told.