Berk, you are just toooo humane. After my father almost died from a pneumonic attack brought on by vacuuming up their mouldy feces I have no sympathy for the dirty little rats.
As to your problem, mice can get through a hole the size of a dime. I'm thinking that your car has been parked for a while outdoors. Park your car in different spots if possible. They will chew through just about anything but metal. They are attracted by food or the smell of food so make sure there is not a speck of food in the car like the hamburger wrappers, milkshake cups, or a package of crackers under the seat. Ultrasonic repellants don't work. Your challenge is to find the entry holes. There should be two or more. Check the fire wall. Check the door seals. Also check any wiring or vent areas for the IMA system under the car. The little rats leave telltale urine dirt paths if they are about for long enough. If you have one you most likely have two or a whole brood. They produce about 40 young a year.
Good luck, Kip
As to your problem, mice can get through a hole the size of a dime. I'm thinking that your car has been parked for a while outdoors. Park your car in different spots if possible. They will chew through just about anything but metal. They are attracted by food or the smell of food so make sure there is not a speck of food in the car like the hamburger wrappers, milkshake cups, or a package of crackers under the seat. Ultrasonic repellants don't work. Your challenge is to find the entry holes. There should be two or more. Check the fire wall. Check the door seals. Also check any wiring or vent areas for the IMA system under the car. The little rats leave telltale urine dirt paths if they are about for long enough. If you have one you most likely have two or a whole brood. They produce about 40 young a year.
Good luck, Kip