Mice built a nest aginst the blower motor speed control resistor, located in the duct where the airflow would cool it. Fire resulted when blower ran on low. Car would have been a loss save for the FE in the trunk, promptly shot into the smoking ducts. Mice also carried a half cup of seeds in. Also ate insulation of several types.

I had mice inside a 960 hoodliner. Good nesting material.

Forget the mothballs. Set multiple traps at one time. They can really mess you up. They can generally go from under the hood to inside the car through the ducts. I know someone who took a dead rat out of a Ford AC, must have been very unpleasant. This was in Florida.

Try to use a long cone type 1/4" HW cloth screen, if there is room. Not just a little piece.

Don't trust those meece!