My mom has a second generation rdx, somehow mice are getting into the cabin air filter and making a nest there. After googling, it seems like this happens with a number of different cars.

I can't figure out how the mice are getting in, or exactly where the intake is on the outside. I don't get to see the car as often as I'd like to figure this out, but I'll see if I can figure this out tomorrow. Just throwing this out there in case anyone else has the same problem, and has figured out a way to keep mice out, or where they might be coming in from.

Mice only need about 1/4 inch gap to get in so that could mean just about anywhere within the ventilation system where there is any kind of a gap.

Thanks for the reply. Today I removed the passenger side engine bay trim panel, and lifted up the cowl panel under the windshield a little bit. It's going to be harder than I thought to try and keep the little guys out. I found the fresh air intake the the hvac system, but I don't know how, or if I will try to cover it with some sort of a screen. I was also thinking about trying to block the path I think they're taking, which is underneath the side engine bay trim pieces, and getting under the cowl panel that way.

I'll have to give this more thought. Back in april the 2 month old cabin air filter was chewed up pretty badly. When I pulled out all the nesting stuff then, it was probably like half the size of a basketball, a lot of material squeezed into a small area. This time around the new cabin air filter wasn't chewed up, and there was less nesting material in there, maybe 2-3 baseballs worth.

The picture of the fresh air intake isn't good, it's basically the rectangular duct you can just see above the yellow line in my poor picture. Second attached picture is what it looked like when I removed cabin air filter in April. It's a bit misleading, because there is a lot more nesting material than you can see when you pull it all out.

Well, here's what I decided to try. Ignoring my crooked cut, just some aluminum screen material attached to the filter with a glue gun. Should work fine, we'll see.

you should put that in the cowl (the aluminum mesh) where the fresh air intake is. That is typically where they make entry into the car...

That was my initial plan. I ended up going this route because the intake is too hard to access, and I basically don't have enough time with the car to tear everything apart, and figure out a way to secure the mesh to the intake.