My wifes SLK200 ( R171) started to develop a nose when heater blower turned on. Went to investigate at the weekend and when I pulled back passenger side carpet I noticed it was soaking. Anyway with thanks to you tube i removed the heater / blower motor and noticed a lot of water damage on it. I gave it a good clean with spirits and cleaned the commutator spindle on which the brushes rotate. I had to use grease to get the clips to slide fully into the rubber mountings, first attempt they were not fully engaged and top of fan was rubbing. Grease did the trick and they pushed down ok. Reassembled and working fine, got to it on time to repair. Anyway went to investigate why water cas coming in and removed the tray above the battery and discovered it half full of water, battery sitting in 4 inches of water. The drain hole blocked with twigs, leaves etc. Cleaned out the drainage hole and put some butyl stick tape across the lower part of the ventilation cut out slot to raise the height of water fill in case it happens again. This will be a regular maintenance item from now on to remove the drain pan above the battery and blow out the drainage hole in the battery well.