Cabin Air Filter Box - What should it look like?

I just checked the cabin air filter in my brand new-to-me 2010 Prius. It's filthy, so I have a replacement coming from Amazon.

Directly above the cabin air filter, there are a series of rectangular holes in the housing that are covered with some kind of black fabric. This fabric is disintegrated or blown out in my car. How should I patch this up? Plastic tape? Is it supposed to be air permeable? I see little push snaps that probably hold the fabric in place - does that mean there are replacements available? (Part number?)

The top of the housing for the cabin air filter is open. There is a pivoting piece at the top with rubber edges that directs incoming air through to the cabin air filter. However there is a huge gap between this piece and the housing for the cabin air filter, at least when the piece is pivoted back. Is this how it should be? Shouldn't it be airtight to the filter area? Or does something make it pivot forward when air is flowing? At first glance, it seems like the incoming dirty air could just flow however it likes within the area behind the glove box. Can someone take a photo of this area for me, so I can see if my car is missing a piece there?

 

I just got around to looking at it again. Here's a photo of the black fabric.

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It's definitely compromised now. It has 3 snaps at the top, so it is replaceable if I can find the part. Or I can try to fashion something out of tape that will pivot inwards, but not outwards.

I turned on the car and played with the fresh/recirc button. On recirc, the top thing pivots back, leaving the top wide open. On fresh, the top thing pivots forward, but doesn't seal against the top of the cabin air filter box. The pivoting thing is geared, so it either left a gap on purpose or the two gears are off by a tooth or two or three. Can someone check their fresh/recirc thingy and tell me if there is a gap when it's set to fresh?

ChapmanF, is that manual available to everyone? I did a search and it seems to be a subscription thing?

 

Hmm. Very possible, now that you mention it. The vertical plastic bar on the left is broken off, but doesn't look like a simple impact thing (why would there be an impact there anyway?). It's blocked in my photo by the top edge of the cabin air filter cover, but the bottom edge of the left side that is open and under the missing vertical bar is rough, like it was chewed on. Researching odor removal, I did come across a thread with a dead mouse and 3 dead baby mice (found after an expensive tear down by service) found in the system. I didn't notice any mouse droppings in the area, but I'll look again.

I can't find the "air inlet control door (sub)" by shape or description on toyota parts cheap or ebay. Looks like I'll have to try to make a substitute. AzWxGuy says that it's a thin foam, probably backed by that fabric I see.

I'll post photos later of the fresh and recirc positions of the air inlet control door on my car so you guys can tell me if looks the same as your cars.

 

It looks like it should be pretty trivial to make a replacement. I'll look for some thin foam rubber with moderate stiffness from already made products/junk (padded stuff like maybe placemats) at home or at the grocery store/Walmart/craft store, cut it into a rectangle of the right size, and then possibly reuse the three existing snaps or just tape it in. I could glue it onto a fabric backing if it looks like it would be needed. It's really easy access the location. I should also improvise a fix for the missing vertical bar to keep the replacement from blowing through.

Here's a backlit view of the air inlet control door (sub), #3 on the diagram that RRxing provided above. You can see where the bottom edge of the opening might have been chewed, along with the broken-off vertical bar and fabric door. Cabin air filter has been removed for the photo. You can see part of the blower fan below.




The top part of the photo below shows the front lip of the air inlet control door, which is edged with rubber (#1 in RRxing's diagram, which is a schematic, not what is really there). This is the fresh air position, as you can see, it is not sealed against what is below it in the fresh air position. Thus recirculated air from the cabin is drawn in from both the (sub) door and the gap at all times.


I think the only purpose of the air inlet control door (sub) #3 is so that, when the fan is off, incoming fresh air goes through the cabin air filter - though some gets into the cabin unfiltered through the gap below the air inlet control door #1, seen above in my car. Maybe this gap doesn't exist in your cars in the fresh air position - can someone please check?

When the fan is on, the suction from the blower below assures that some cabin air is recirculated through the air inlet control door (sub) #3, in both the fresh air and recirculated modes. If I keep the fan on, I don't need to fix that flap.

Thoughts about mice: There is an odor that I'm trying to eliminate. In the "Need help assessing possible problems" thread, I thought the odor was probably from water that had been sitting in the spare tire well for possibly years. But it could a dead animal smell from the vents. I don't notice additional odor when the fan is on, or from the vents specifically, but it's hard to elminate the possibility. If a mouse entered the HVAC system through the hole in the air inlet control door (sub), it would be blocked from going below by the cabin air filter. If it chewed through or slipped around the cabin air filter, it would be blocked by the blower fan. Maybe I'm underestimating how narrow a gap a mouse can pass through, but maybe that's as far as it would go. What's next beyond that? The heater core/air conditioning evaporator box? I did see a photo of that accessed by removing the passenger side heating vent in one of the Kool It AC cleaning threads. Maybe I'll try to get that opened up and peek in there. Going the other direction, wouldn't it just lead up towards the outside air inlet below the right side of the windshield, which is screened anyway?

Give me your thoughts please. Overall, I don't think there's much of an issue, even if I don't fix anything other than changing the cabin air filter.

 

Correct.