This is an old thread. But I have this issue and am not able to find where the hole is under the driver side dash. . I've found where the water leaks from which is close to the condensation box, but not the hole. . I know where the drain hole is on the outside in the engine bay is though. . I shoved a untwined hanger in it. Other than that I have some flex seal ready for when I finally figure out where to 'seal' the inside of my car.