I had mice nesting under the cabin air filter and the engine air filter in three different cars. In one car (VW) they ate holes in insulation attached under the hood. These are cars driven daily.
Moth balls did seem to work but I hated having the car smell like a old person's closet. I switched to peppermint oil (got from Amazon). Sprinkle some on the air filters once a month or so, no more mouse problems in over a year.
Downside is the first time I do this treatment I have to drive with the windows open for a while till the smell dissipates.
I also used traps but mice reproduce so fast it seems futile. DON'T use poisoned bait unless you don't care about injuring/killing the hawks, owls and eagles in your area.