[XcitR]

I'm stumped! I have a 91 Sierra that has been getting a wet floorboard on the passenger's side whenever the A/C is run and the floormats are used. I've tried the A/C condensation drain, heater core, even replaced the lower heater cover (which was cracked), thinking it was condensation from the escaping heat. The substance is definitely NOT coolant... and seems to be water. It's not the windshield leaking, and isn't related to if it rains or not. I get the same situation with 2 weeks of no rain and 90 degree weather.

As a further test, I laid a 6" x 6" piece of thin rubber/nylon material on the floorboard in place of the mat, and the carpet was wet ONLY under the test material! I can't think of any other possibilities. Anyone out there have any ideas?