This is interesting. The only way into a “properly adjusted and closed” 1967/68 Mustang Coupe or Fastback is through the cowl drain openings at the far side of cowl area, up and under the back of the front fenders. If the trunk lid is tight and the doors are tight this is really the only way in. I know mice will surprise you on how small a gap they can get through, but I doubt they can squeeze between the cowl “grill” openings at the base of the wind shield. GT/CS trunks are fun to seal sometimes.
So with that, if the driver air vent is shut and in good condition, my thought is the mouse cannot enter and chew the plastic grill bottom of the vent to enter the interior.
That leaves the cold air entry to the heater assembly. On a non-air conditioning car, you can open your vent door by the right kick panel and actually reach up into the cowl area. This is the only route for “Mickey” to find his way in. If push up all your heater controls to the off position you will see a door close to the heater core. If fully closed, Mickey cannot enter the core and come out the center heat vent into the car. So always store your car with the heater controls in the close position with the driver air vent closed and the heater off.
You can actually put a small mouse trap or decon inside the passenger vent door and then close it. Check it every so often. If you are restoring your car, and the front fenders are off, you can weld a screen with say ¼ mesh over the cowl drain holes. These openings are the cause of many a Mustang to rot and let mice in.
A word of caution is if you put screens on them, they will be easier to plug with “stuff” coming in the cowl grills. Then water stands and you rot away. A quick way to check them is to have the car on the level and pour a large glass of water carefully on one side of the cowl grill. You will be standing right behind the front tire to do this. If your feet are slightly under the car, have a pair of open toed sandals on. You should be treated to wet toes as the water drains on your foot. If nothing comes out, you better clean those drains immediately so you can freeze your toes!! Or it went straight into the interior.
I do this on all Ford unibody cars I look at for people or myself. Have someone look in the interior on the front floor as you pour. If water comes in the interior you got some cowl problems and more than likely floor pan rot!!
Rob
