My Ford Freestar had a mouse nest in the airconditioner. Had it removes and the back bumper vents plugged. Have another dead mouse. How are they getting in? How do you remove the door panels to find them?

Unfortunately, they could be getting into your vehicle any number of ways since they can chew through pretty much anything...

For the door panels, you can remove screws that are by the door handle, arm rest, under door and side of door and then gently pull back on the panel as there will also be retaining clips attached and you don't want to break them. You'll need to lift the door panel upwards in order to get it off the window ledge.