# Mice getting into HVAC system



## cyteen (Dec 18, 2015)

I have a 2014 Chevy Cruz LS 1.8. With the hood up and looking at the firewall, there is a HVAC duct with a flap covering it a little to the passenger side from the middle and less than a foot from the top. This duct runs at least to the cabin air filter. A mouse entered here (pieces of filter were found under the flap) and made a nest on top of the filter where it then died! I went to the dealer that we purchased the car from and their service dept. tech. manager did not know what it was or it's function. When asked if the flap could be wired shut to keep mice out, he said he saw no problem in doing so. It seems like GM needs to come up with something to prevent this problem.


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## spacedout (Dec 7, 2010)

That flap is part of the drain system for the cowl area.


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## Robby (Mar 1, 2013)

Not a GM problem......you are parking your car in an area that is not far from a food source.
Mice don't select a car as a home, mice select any warm, protected area near a food source as a home.

Doesn't much matter what brand of car.
However, when mice (or any other rodent) take up residence they often use any available nearby area to chew on and sharpen their teeth....think wire harness or hard plastic as found in a heater box.

Most common draw point for mice......seed kept in a garage in the off season......grass seed is their favorite.....if you can smell it, they really can smell it........doesn't have to be your garage either, a next door garage works just fine.

All cars have a drainage system in the air intake area......the Cruze has a central drain (that you describe) and at the sides of air intake box, either side of the box, hidden by the front fenders.

I have been removing rodent nests and undoing rodent damage for years.....one more unique experience that comes with auto service trade......often out of the hvac system and sometimes in semi enclosed underhood areas......in no case have I found rodents picking a particular brand or model vehicle.

I recently pulled a nest, that included live newborn squirrels from behind the drivers side headlamp area of a Hummer.
I had a Clark Griswald moment as I reached in when I saw beady eyes along with squealing........at my age, I don't need those moments.
Anyways, I don't think they chose the Hummer by brand.

Look around your current parking area.....there is a clue somewhere.

Rob


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## spacedout (Dec 7, 2010)

Robby said:


> Not a GM problem......you are parking your car in an area that is not far from a food source.
> Mice don't select a car as a home, mice select any warm, protected area near a food source as a home.


Park within 100 feet of a bird feeder or any seed or nut bearing tree you could get rodents. With my cruze its the same problem I've had with my previous cars..... Squirrels. Pulled 5 walnuts out from various places under the hood when I changed the air filter this fall. 

With both my 1991 Lesabre and 2004 Cavalier squirrels managed to place walnuts within the travel of the throttle body. Not fun when the soft green skin of the nut allows you to open up the throttle but wedges it at 1/2 throttle or greater! When it happened once I thought it was a crazy coincidence, after the second time I realized the squirrels murderous intent.....

I had a neighbor eliminate about 20 squirrels with a pellet gun and poison but more just move in since there are no real predators in town.


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## brian v (Dec 25, 2011)

So are we going to laugh yet ????????????????? 
Get a CAT !!!!!!!!!!!!!!!


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## NickD (Dec 10, 2011)

Not a darn thing I can do with the engine compartment on my motorhome, find a squirrels nest there every spring, everything else dealing with the interior, added screens. How about finding a live wasp nest in the range hood vent, they don't even think about stuff like this when they throw them together. 

Installed my own high efficiency furnace using 2" high grade PVC tubing, heard about birds or mice crawling into these keeping your furnace from working. Got a couple 2-4" adapters, put them in my lathe and cut a ring. Using a 1/4" screen for an outward pointed exhaust and a fine mesh screen facing down for the inlet, after six years so far, never had this problem.

Getting back to the Cruze, part 7 is the cowl bladder for drainage, is yours there?










Just like anything else, just slips on, no clamp. Is a five buck part.


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## Tomko (Jun 1, 2013)

cyteen said:


> I went to the dealer that we purchased the car from and their service dept. tech. manager did not know what it was or it's function. When asked if the flap could be wired shut to keep mice out, he said he saw no problem in doing so.


This is a person that should have no employ with GM or a dealership. Let alone a leadership position as manager. 

This is person has no clue what the part is for. Yet he knows that it can be defeated without consequence. 

Ladies and gentlemen: this is what a dumb person sounds like and how the think. 

An intelligent person would have said: I don't know what that part is for. But I do know that the engineers who designed this car decided that it needed to be there. Despite the cost, weight and collision implications of its installation. And therefore, for that reason, I cannot agree to remove, alter or defeat it. 

The minute a technician permanently removes a part that my vehicle left the factory with, or even suggests it, without a TSB or recall instructing to do so, is the moment that a letter is written and that technician never gets near my car again.


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## brian v (Dec 25, 2011)

Shoot tomko , I really do not believe any such Tech exists that knows how to keep menacing mice and squirelly squirrels along with the occassional pesky Raccon that wants to utilize yer ride for a hiding place for IT's foraged food stuffs ..


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## NickD (Dec 10, 2011)

Well, maybe the engineer that designed this thing wasn't so smart have all, instead of using a conventional rubber one like a balder. Using a piece of plastic with a door on it. Can see where an industry mouse could stand on that AC hose, push open that door and crawl up. 

Could put a chicken wire screen around it so the door could still be opened, but sure don't want to wire it shut, all that water will end up in your interior. Or go back to the design that did work. Here's another stupid solution that may work, get a hack saw and cut off that AC line so they don't have anything to stand on.

A buddy down south opened the hood on his 37 Ford coupe to see a rattle snake coiled up on his engine, thought me to look first before reaching in. Just looking for a nice warm spot.


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## cyteen (Dec 18, 2015)

Thanks for the responses. Here is the flap that covers whatever this outlet is. This is where we found shredded cabin air filter material.









Is this part of the HVAC system or just a rain water drain? We came across that diagram but the way it is drawn it unclear how and where that drain attaches. It is also unclear how the mouse could have gotten from there to the cabin air filter if this is just a rain water drain.


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## Robby (Mar 1, 2013)

It is one of three drainage points for water.
Debris that has been dragged into the cowl area will naturally get drawn to and accumulate to the lowest part of the cowl.
The entire cowl area is used to house and protect the windshield wiper pivots and linkages as well as provide a air pickup point for the hvac system.
This is a common construction method for all vehicles.

Using Nick's provided component breakdown, component #9 represents the end drains and is spot welded to #6........you can see that the cutout does not go all the way to the bottom of the chamber (#6)

This would be why the triangular drain that you (op) have provided a photo of, is necessary.

Although you see debris at the drain, the critter most likely is climbing up the various brackets and whatnot behind the fender and into the chamber through the large end plate hole (#9).

Regardless of entry method, you must determine what is drawing critters to the area your car is generally parked at........either at your home or where the car is during the day.......and then figure out how to avoid the situation.

Early evidence is the debris you found........over the long term the vehicle will be damaged.......wireing chewed, hvac components broken or blocked, and oder from excriment.

Just reading my newest Car and Driver......one of the editors has a Tacoma and has developed a mouse problem.......evidence has little poo balls all over his sheepskin seat covers and he has been setting traps in the car......reported has gotten two so far and hasn't figured out what is drawing them......yet.

Rob


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## NickD (Dec 10, 2011)

Added a list of parts to this cowl assembly. Without taking stuff apart, unclear to me if this cowl assembly is metal or plastic, seems to be plastic. I see only one drain on mine, if I took a photo, would be exactly like yours.

These critters can squeeze through the tightest spaces, for the first time I found my toilet paper all chewed up inside the rear sink cabinet, just drilled an oversized hole for the plumbing, how in the heck did whatever squeeze through that. Another hole to patch in my motorhome.

Like Robby was talking about, also experienced wire damage by these critters, but only the green wires, must have mistakened this for food. 












1  95321394  COWL GRILLE, RIGHT $128.80$86.55 
 1  95321393  COWL GRILLE, LEFT $128.80$86.55 
 2  95230842  COWL GRILLE RETAINER, RIGHT $3.82$2.44 
 2  95230842  COWL GRILLE RETAINER, LEFT $3.82$2.44 
 3  22745468  PLENUM PANEL $70.63$47.47 
 4  93740116  PLENUM PANEL INSULATOR $34.03$22.87 
 5  96899408  PLENUM PANEL REINFORCEMENT $9.25$6.22 
 6  22756012  UPPER DASH PANEL $107.38$72.16 
 7  13360834  DRAIN VALVE $7.70$5.17 
 9  13328635  SIDE BRACE, RIGHT $15.13$10.17 
 9  13328636  SIDE BRACE, LEFT $15.13$10.17 
 10  23426232  INSULATOR INNER
$86.33$58.02 
 11  22829812  INSULATOR OUTER
--


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## Robby (Mar 1, 2013)

With the exception of #'s 1-2-7-4(plastic) and #'s 10-11 (insulation pads) all panels are steel and are spot welded together.

Difficult picture since some illustrations are as seen from front others from rear....specifically #10 insulator.....that's the pad attached to the toe panel (firewall) on the inside, under the carpeting.

Although not shown in the figure #8 (toe panel) is serviced as an assembly that would include both #9's, #6, and #3 already spot welded in position.

Rob


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## cyteen (Dec 18, 2015)

Robby, thank you for your response. How would you access the #9 end plate holes? Could they be made smaller? Or wire screening?

Also, thanks NickD for the parts breakdown.


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## Jim Frye (Mar 16, 2011)

D-Con? Yeah, I know everyone hates poison, but the stuff does work if you apply properly and safely.


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## spacedout (Dec 7, 2010)

What about the soy based bio-degradable wire coating that is an attractant for rodents? I always heard some brands were more effected than others, but it sounds more like all manufactures are utilizing this type of stuff now. 

Here are a couple websites with more info, the second one has some things you can try to rid your car of rodents.

Incredible Edible Car

Mice eat new car&apos;s wiring, cayenne pepper to the rescue - Chicago Tribune


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## Robby (Mar 1, 2013)

cyteen said:


> Robby, thank you for your response. How would you access the #9 end plate holes? Could they be made smaller? Or wire screening?
> 
> Also, thanks NickD for the parts breakdown.


The item #9, endplates are covered by the front fenders......fender removal required to fully expose but you may have just enough room to access (no promises here) by removing the front wheel(s) and plastic inner fender liners.

Rob

Edit: a different route may be to remove the wiper arms and both halves of the cowl cover.....look/reach inside.


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## roadrunnerA12 (Jan 21, 2015)

I can't believe that the other cowl drain outlets on my Cruze are large enough to let a mouse in, but this one sure is. Do other GM lines have this "flapper valve" drain? Just changed my In Cabin Air Filter to get rid of the stench from a mouse nest on top of it. I am going to drill a vertical 3/8 hole thru the top and bottom of this culprit and wire it shut. I will remove the wire every so often (maybe twice a year) and let the crap out that has fallen down from the cowl area. 
[video]https://www.facebook.com/jrsharland/videos/1080737171960596/[/video]


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## Robby (Mar 1, 2013)

The end cowl openings covered by the fenders are large.....like 4" by 4" large........All manufacturers btw.

Rob


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## NickD (Dec 10, 2011)

Remove those plastic caps from the windshield wipers, a couple of screws, off they come, rest is all push pin rivets, don't want to lose any of those, my dealer charges around four and half bucks for each of those, at that price and at the OE level, would expect to get a package of a thousand for that price. Then part #1 is in your hand.

Just don't recall seeing holes in those #9 end plates, maybe I didn't even look, but really doubt if they are there for drainage, way too high. If they are there for any reason, would let more air in in the event if that #1 vent, only on the drivers side is plugged with ice and snow. 

If anything, would hot glue chicken wire to those openings to block entry. Actually found plastic at my hardware store for the intended purpose of keeping leaves out of your rain gutter. Used this on my exhaust vent for my furnace, lasting for years, galvanized wire would rust through leaving a large hole in a couple of months.

Some vehicles I had used vent holes so large on that cowl grille, leaves were dropping in plugging up the drain hole, had to add a screen to those, Cruze does not have this problem. Most ran that drain tube down to the bottom, road salt splashes up on your windshield, drain for the Cruze is way to high, that crap will end up on the engine block causing more corrosion. 

Always post production work to do if you want your vehicle to last a couple of weeks longer than the warranty period.


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## Robby (Mar 1, 2013)

Nick,
The plastic screen stuff for rain gutters is, IMO, a great option.......cut to fit in the end plate holes, would not promote rust and would prevent critter intrusion......inexpensive too.

Sold in four foot lengths....should be enough for the next ten cars.

Rob


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## NickD (Dec 10, 2011)

Got an 8" wide 20' roll of the stuff for under three bucks from Fleet Farm, only needed 5" of the stuff, but needed it. Could donate it to the cause, but the cost of envelopes and mailing would be prohibitive.


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## roadrunnerA12 (Jan 21, 2015)

So, can anyone tell me if other GM vehicles have this exact same "flapper valve" drain on the firewall that opens up large enough to let a chipmunk in? The small Buick? The small Cadillac? The more I think about it, noting how much that flap lifts up on it's hinges, I could have had a chipmunk nesting on the In Cabin Air Filter, but there were no turds in the flutes, just urine, so I couldn't to a feces size/shape analysis for mouse vs. chipmunk.


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## spacedout (Dec 7, 2010)

My car sits outside 100% of the time, and always find a ton of leaves on my cabin filter because of it. After the first 1.5 years of ownership, I noticed that drain on the firewall was stuck wide open with old rotting leaves and debris. My guess if rodents were getting in though that flap, it was because like mine it was jammed open in the first place.


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## Robby (Mar 1, 2013)

I am confident the critters are going in through the side openings.....can't imagine a mouse going through the acrobatics and effort to get in that way.

Rob


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## spacedout (Dec 7, 2010)

Robby said:


> I am confident the critters are going in through the side openings.....can't imagine a mouse going through the acrobatics and effort to get in that way.


That's exactly what I think as well, however if that flapper is blocked wide open something could get in that way. just take a few minutes to ensure the drain flap isn't stuck open. Much more likely they could enter that way if it is just an open hole(flap jammed open). 

The OP mentions finding cabin filter pieces under this flap, since this is the drain point any pieces the mice have spread in the cowl would end up at this drain eventually.


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## NickD (Dec 10, 2011)

spacedout said:


> My car sits outside 100% of the time, and always find a ton of leaves on my cabin filter because of it. After the first 1.5 years of ownership, I noticed that drain on the firewall was stuck wide open with old rotting leaves and debris. My guess if rodents were getting in though that flap, it was because like mine it was jammed open in the first place.


How in the world are you getting all the leaves in there? Is somebody ironing them flat and carefully sliding them sideways through those thin slots in the cowl grille?

With that drain door wide open, can't even squeeze my baby finger up there. But that space where the that pipe comes up through the floor in my motohome was even small than this. About 3/16" width.


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## spacedout (Dec 7, 2010)

NickD said:


> How in the world are you getting all the leaves in there? Is somebody ironing them flat and carefully sliding them sideways through those thin slots in the cowl grille?


No idea, all tiny pieces of leaves. all the pleats of the cabin filter will be 60% ore more full every fall after the leaves stop falling. Have founds some pieces larger than a quarter laying on top the cabin filter and a few trying to make there way past the filter on the door edge(where you change the filter). 

The nasty sludge I found at the firewall flap was very broken down wet leaves, probably similar size pieces as the cabin filter gets plugged up with.


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## NickD (Dec 10, 2011)

spacedout said:


> No idea, all tiny pieces of leaves. all the pleats of the cabin filter will be 60% ore more full every fall after the leaves stop falling. Have founds some pieces larger than a quarter laying on top the cabin filter and a few trying to make there way past the filter on the door edge(where you change the filter).
> 
> The nasty sludge I found at the firewall flap was very broken down wet leaves, probably similar size pieces as the cabin filter gets plugged up with.


Heard rumors about gremlins, but haven't seen them yet.


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## cyteen (Dec 18, 2015)

Hi guys, thanks for all the info. We had a chance this morning to remove the passenger side cowl, it was not necessary to remove wipers to get it off (3 fasteners). This is how the central outlet drain is attached.










The large object above it is the air inlet to the area above the cabin air filter. This is where NickD's screening would go to keep a mouse away from the filter and HVAC system.









The fender drains Robby was talking about are about 2x2 inches on our car.









The lines nearby the flap are very easy for a mouse to stand on and get to the flap - about an inch to the braided hose to the side and about 3 inches to the big A/C hose underneath. 









Whether the mouse came in through the fender drain or the central drain, putting NickD's screening over the air inlet by the filter would keep mice and other debris out of the HVAC system.


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## ChevyGuy (Dec 13, 2014)

NickD said:


> If anything, would hot glue chicken wire to those openings to block entry. Actually found plastic at my hardware store for the intended purpose of keeping leaves out of your rain gutter.


The only thing I worry about is that critters might chew though plastic. Decades ago I know I saw the same thing made from aluminum. I'd think that would be more critter resistant.


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## spacedout (Dec 7, 2010)

Sure they could chew though the plastic, but at least it would slow them down unlike the wide open hole there now.


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## reno4zr (Apr 3, 2011)

I actually had the same issue on my 2011 Cruze. I tried the decon and it worked, but you can imagine the smell of dead mice coming out form the vents for some time.. 








I ended up covering the cabin intake port ( I borrowed the previous picture so other would know what "port" I was talking about.








with piece 1/4 inch galvanized wire mesh I got at the local hardware store. I cut and bent the piece to fit, then fastened it with self tapping screws to the cabin intake. I don't have a picture of this finished, but it has been over a year without anymore mice. I would not try to block all the individual drains as the mice will find another way up to the big entrance....


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## roadrunnerA12 (Jan 21, 2015)

Indeed the fender drain openings are big enough to let in a small dog, but what about the actual outlet points down lower for these drains - how big are those openings? Too lazy to pull a front wheel and pour some water down the cowl to find out. Anybody know?


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## Robby (Mar 1, 2013)

The big end openings just dump inside the fender......no channels, just gravity.

Rob


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## Robby (Mar 1, 2013)

Kinda weird......I'm bouncing between the Miata forum and this one this evening.

A guy posted, with pictures, a shot of a rat, dead in the squirrel cage of the blower with the same 'how'd he get there?' questions.
Miata's don't have cabin filters so this big boy just went up inside the fender, through the big end openings, and evidently fell down the inlet hole, right into the squirrel cage.

Car had been parked a few days.....rat evidently met his maker at some point.....when the owner drove the car and turned on the blower it vibrated......a lot.
He dropped the blower and 'surprise!'.........heh heh......I think just finding droppings and debris on the filter is OK in comparison.

Rob


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## Jim Frye (Mar 16, 2011)

Nostalgia time. My first car was an '62 Impala SS. It sat outside 'cause Mom & Dad's cars were in the garage. One cold morning, I went to leave for school, cranked the engine and heard a "thump da bump de bump" from under the hood. Shut down and opened the hood to find the neighbor's long haired cat wadded up in the space between the headlight and the fender well with most of his under-hair missing. Seems he crawled up on the warm engine for the night. The only way out was to go over the generator. The belt mist have grabbed the hair and tossed him aside. He was PO'd and lept out of the engine room making a straight line back home.


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## NickD (Dec 10, 2011)

Ha, don't even get me started with that motorhome, MVAC was loaded with that stuff. Under that eight foot wide dash panel was a huge piece of plywood that was installed before they fastened the entire fiberglass front. Had to cut that down the middle to remove it to get to all that MVAC ducting. Was a home for these critters.


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## spacedout (Dec 7, 2010)

I bought a cheap used 1986 Buick Lesabre once that needed some work. After a month in a friends garage when we finally went on the maiden voyage got about 10ft and entire cabin filled with smoke. Pulled the squirrel cage and found it completely packed with a mouse nest, which somehow had cough fire.


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## foghorn14 (Jul 4, 2015)

I hate to revive a five month old thread, but I thought it was better than creating a new one. Add my name to the list of Cruze owners who have had a mouse infestation in their car. My culprits seem to have found the central drain (see pic below) as it was surrounded by their mess. The intake for the HVAC has to be one of the dumbest designs I've ever seen. The GM bean counter that saw fit not to cover the intake with some sort of grille or mesh should have the five dead baby mice I found in the intake and on top of my cabin air filter mailed to him. Thankfully they didn't seem to have made it beyond the cabin air filter further into the HVAC system. 

Anyway a good cleaning out the with shop vac and all the mess was gone. I went and bought some wire mesh rat wire and covered the intake securing with self tapping screws and silicone. While I was in there I went ahead and covered the central drain and fender drains with rat wire mesh as well. I hope my "engineering" fixes this so that it doesn't happen again. Other than the mice mess there wasn't a bit of trash in the cowl... we don't have any trees so I don't expect any problem having the mesh over the drains.

Anyway thanks to everyone who posted in this thread. You made fixing this mess a not so pleasant breeze. (No pun intended) Hate to think what a dealer would have charged. 

Anyway here's some pictures of the lovely nest I found in the car.






















Oh BTW special thanks to Reno4zr for the idea about the 1/4 inch mesh.


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## mod (Apr 21, 2017)

Well,it was my turn this time...a large RAT in my 2012!
Comprehensive covered the cleanup an shampoo for the seats and carpets.
I slid a stainless plate with small holes in it in with the filter.
This will keep them from ripping out the filter and getting in.

Thanks for all who posted!


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## Trtmntdude (Sep 19, 2011)

I know this is an old thread, but I didn't want to start a new one unnecessarily. I was cleaning under the cowling after the car had sat for a few years while I was out of Country, and I found this. I had also changed the cabin filter and saw what I now know was nesting material from a mouse/rat. They used the louvers to sharpen their teeth. Is changing the air inlet box very hard?


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## Blasirl (Mar 31, 2015)

Trtmntdude said:


> I know this is an old thread, but I didn't want to start a new one unnecessarily. I was cleaning under the cowling after the car had sat for a few years while I was out of Country, and I found this. I had also changed the cabin filter and saw what I now know was nesting material from a mouse/rat. They used the louvers to sharpen their teeth. Is changing the air inlet box very hard?



This will get you started


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## Pete in PA (Dec 1, 2012)

Wish I'd have done a search years ago for this thread. I have 2 Cruzes and combined found probably 7 nests on my cabin filters. I never change a filter for just dirt, no time. Of course when you pull the filter all the mess goes down to the blower fan. I got good at pulling acorns out of it so it wasn't out of balance. Never thought to remove the plastic cowl covers and attack the problem from there.

I live in the woods, lots of acorns for the mice to eat, can't stop that. Just have a carport.

Going to Tractor Supply today to buy 1/4 in. mesh. 

I think the default mode after the car is off for 10 minutes is the outside fresh air door shuts. I've got a small hole chewed through the door.

And yes I've got MORE cabin filters on order.

I wonder if this thread should be linked with this one. FIX: Excessive Moisture/Condensation/Frost on Windows
Doors get out of sync from debris, whether natural or mouse related. Those acorns can really stop the door.


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