Wet Passenger Floorboard

[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?

[PeteA216]

Run your A/C (let it really cool off) and watch under the dash above the floor, and see if you can find anywhere where the water seems to be coming from. My guess is that its just condensation from your low pressure a/c line that could be dripping down your firewall, and onto the floor. If this is the case, you might want to try to insulate the line.

[batt75]

look under the hood where the two heater core lines are there should be a small piece of tubing there also does it come straight out or does it come out and have a piece of rubber hose that turns 90 degrees to the ground if it is missing the hose go to the parts store and get one had same problem on my truck floor would only be wet when i was driving for a while but i could leave it running for hours in the drive but the floor would stay dry, guess air passing over a straight tube will not let it drain but a 90 degree turn will. try and let me know