Rats can enter through the Re-circulation Air vent beneath the plastic cladding beneath the bonnet. To access it open the bonnet and find the black plastic stuff with vents, unscrew it and you should be able to access the vent. You should probably seal it with wire mesh and then rats wouldn't be able to enter the cabin at least. Somewhere in the forum Grandeur has posted the pictures of the exact location. Will post it if I find it.