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    luckyflyer Junior Member

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    Anyone know which way the arrow points on an aftermarket cabin air filter such as say a wix or fram or other? I'm told that the arrow on an aftermarket filter indicates airflow direction . That would mean that on my 11 prius the arrow would point down instead of up as with the oem filter. The wix filter that I have does not address the arrow direction anywhere on the box.
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    The Critic Resident Critic

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    The arrow should point down. I am using a Wix charcoal filter from an IS250, and the charcoal side is facing up.


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    jdcollins5 Senior Member

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    +1

    I am using a Fram. The charcoal side is also up and the arrow is pointing down.
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    luckyflyer Junior Member

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    Thanks, the wix filter that I have (24483) is not a charcoal filter. Both sides look the same. You would think that wix would mention the arrow somewhere on the box.
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    Bill075 Junior Member

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    I called Wix Customer Service last week at 704 864-6748 and was told the arrow points up.
    Everyone should call and see how many ups & downs we get, or does it really matter on the wix
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    jdcollins5 Senior Member

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    Part of the confusion comes from the Owner's Manual that shows the cabin air filter arrow pointing up. IIRC even the outer plastic cover has the arrow pointing up. But the manual also shows blowing air to clean in the direction of the arrow indicating that any dust and particles would be on the top side of the filter ;)

    The air flow is actually down as it is drawn from the outside, down through the filter and then blown into the cabin. When looking at the air filter when removed the dust and particles will be on top of the filter indicating air flow in the downward direction.

    There has been many threads on this subject when the Gen III first came out.
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    luckyflyer Junior Member

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    So I guess the big question is does the arrow indicate air flow direction on aftermarket filters? Based on what others have said I must conclude yes to that question. Thanks for all of the input on this.
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    jdcollins5 Senior Member

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    IIRC the Fram filter actually states "Air Flow Direction" next to the arrow. Also, if IIRC, the OEM filter did not have any markings next to the arrow to indicate the meaning of the arrow.
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    El Dobro A Member

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    Just checked the filter today and it says "UP" next to the arrow.
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    jdcollins5 Senior Member

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    What filter do you have? OEM?

    What does UP mean, other than the arrow needs to point up? It is not a good indication of air flow direction.
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    El Dobro A Member

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    OEM filter and to me, UP means to stick the filter in the slot with the arrow pointing up.
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    jdcollins5 Senior Member

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    This is where the confusion comes in for someone using non-OEM filters with air flow direction arrows. The air flow direction is actually DOWN and not UP.
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    El Dobro A Member

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    If I bought an aftermarket filter, unless it had the word airflow and an arrow printed on it, I would put it in with the arrow facing up.
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    Bill075 Junior Member

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    Why try and second guess what the manufacture means... if no clear instructions are given call or email the manufacture tech dept.
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    jdcollins5 Senior Member

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    You can always do that.

    The easiest way though is to pull the air filter and see what side has the dust and particles. This will be the upstream side of the air flow. In the case of the Prius this will be the top side of the filter, indicating air flow is in the DOWN direction.

    Another way to look at this is that if the air flow was in the direction of the UP arrow, then every time the blower motor stopped the particles would fall back down into the blower motor :(
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    El Dobro A Member

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    Looking at the filter, I don't see what difference it makes on how it goes in.

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