About a month ago after I had pulled into the garage and taken the key out the interior Warm Air Recycle function came on by itself and ran for about 10 seconds with no lights on. It then did the same thing about 30 seconds later.

My first thought was the climate control unit so I called the local MB dealer. They wanted $1,200 plus install. I located a used one on eBay from another 2008 ML and spent $200 which includes a one year warranty from Square Trade. I put it in myself - thank you YouTube.

All OK for about a month then it happened again last week. Spoke to my long time MB Indy who told me the blower motor would be suspect as they are prone to getting moisture in from going through a car wash with high pressure. I always switch to the Interior Air Recycle mode but who knows. Mercedes wanted close to $500 plus the Indy's one hour install. I located a new, genuine MB unit on eBay again, skipping the Chinese copies, and paid $390. Found another YouTube video and installed it myself.

I was actually going to have my Indy install it and only found the video after I ordered the new blower motor unit. In the video the guy showed how you can remove the circuit board cover on the unit to see if moisture had caused any corrosion. After I had installed the new unit I took the cover off the old unit and presto - a little bit of corrosion on four different contact points. Took some isopropyl alcohol and q-tips and cleaned them right up. If I had known about this earlier I would have tried the cleaning, but anyway, I now have a spare that might be OK and a spare climate control unit :^)

One thing I did notice on the new unit was a drain hole in the section directly under the cabin filters.

Here is the video I found:
Hopefully this will help someone else.