170 slk. I was having an intermittent fan, sometimes it would work fine other times not. first it wouldn't run, after a few minutes more or less it would come on again and be fine till the next time I jumped in the car and fired her up. I replaced the resistor on the motor and so far no problems. Two Phillips screws holds the panel in place just under the glove box. find a couple vent holes in the panel to put your fingers into and push toward the front of car, then pull down, pull towards rear. the blower box has a couple slide clips. you'll need a, I believe, a #20 torx to remove the resistor. on re-installing, there are two clips toward the front of the car on the panel attached below the glove box. those need to be put into the slots for them under the dash. having a mirror helps the whole process. resistor varies in price from around $25 to $125. I paid $29 and it looked the same as the old one. my F150 just had the same problem. might be interesting if mercedes put their twist on a f150 and put their name on it. the 150 is a great base for a merc truck.

 

same problem; fan brushes sometimes don't make contact with brush holder; noticed armature? had some wear on it; so just changed complete motor; aftermarket WAY less than $100, now ok; also got new resister on it, but DON'T think it needed it; keep for spare; hope this helps, Steve

 

I forgot to mention on mine the higher speeds worked ok, indicating the motor was ok. looking at the resistor you could see where it was loosing continuity. the finish was lifted like rust under paint on one of the printed circuits