I've seen all the posts about the clogged AC drain but I can't believe that is the source of my problem. It always happens after a heavy rain, I get about a gallon of water on the passenger side floorboard. I don't get any wetness when running the A/C. I've checked all seals around the front window and doors. I have also dissambled the plastic grill under the wipers and found the vent holes at the top of the firewall that go into the interior of the car. Here is my theory. During a heavy rain the water runs down the windshield and over the plastic vents under the wipers. This water is supposed to drain off along a tray just below the air vents on the firewall. The tray leads the water to a drain hole on each side of the car by the fenders. During a heavy rainfall the amount of water draining off the car is too much for the drains to handle and rainwater is backing up through the outside air vents. My question is if this is what is actually occuring, can that water make its way down through the ventilation ducting and leak out through foot register on the passenger side? Just worried if I test this I run the chance that I do get some water in the AC or blower and cause electrical damage. Does anyone know how the ducting runs on the interior of the car?