Hello,
My 2012 GL450 seems to be dripping water from the underside of the dash on the passenger side. It drips on my feet when I'm sitting there while my husband is driving and we have the air conditioning in. This doesn't seem normal. What could be wrong?

 

I've not experienced it on my Mercedes, but on another car this was the drain tube being clogged with debris. I don't know exactly where it is on this vehicle but perhaps somebody knows. The way to check would be to run some flexible plastic wire (like weed whacker line) up the tube, or to use compressed air to clear the obstruction.

If you or your husband aren't the type to crawl under the car, a local mechanic should be able to determine if the line is clogged pretty quickly.

 

Had exact same problem in an older ML. Turned out to be some kind of drain tube that had to be replaced. Dumped water on the floor or passenger's feet when I went around corners. Don't remember any of repair details though