Why does the floor of my 2015 Mitsubishi ASX, both under and behind the driver's seat, get wet whenever I drive in the rain with the windows wound up?
It’s amazing where rainwater will get to under the influence of a pressure difference between the inside and outside of the car, not to mention a 100km/h gale trying to blow everything inside the car. As such, you only need a tiny tear or crease in a door rubber for water to enter the car. And if it enters somewhere near the driver’s seat, that’s where it will stay when it hits the carpet.
Check the rubber seal in the door opening for any signs of damage or a small chunk missing. Even a piece of leaf debris stuck to the rubber can allow a gap big enough for water to enter. Make sure, too, that the door itself is properly aligned on its hinges and is making contact with the whole of the door rubber when it’s shut.