I pulled up the carpet on front passenger side of my 300E yesterday by chance, to find a pool of water under the floor carpeting, mostly soaked up by the "sponge" under the carpet.

I checked under car in that area and couldn't find a missing grommet that would allow water in from outside.

Anyone know the possible cause here? Is there a drain hose, or AC line that runs past this area? All I could see were various wiring that luckily are wrapped in waterproof taping, however there's a switch down there that is corroded and ruined. (think its stereo related)

TIA