I've had an intermittent blower motor for the past few months. No mater what mode I was in, automatic, manual or defrost, it would either work or not. Also, on occasion, my fan would start working after I hit a bump in the road. Finally last week it quit altogether. I can still hear the vacuum mechanisms move when I press the different climate control buttons, but no fan. Is there a hidden fuse or relay somewhere, or any other places to start investigating. Thanks

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2012 550CLS
1982 380SL
1985 300D
1998 ML-320
1997 E-320
1984 380SE

Same thing happened to me and it turned out to be the blower motor. I opened mine up and the brushes were worn down so there were barely making contact. I found some brushes thar were close to fitting and modified them to work. That was 3 monthes ago and since then I purchased a new blower motor with the thought of replacing when weather turns warmer. You can buy a neew motor without blower for under $100. and then just swap out the blower.
Hope this helps, this had me baffled for a while.
My car is a 83 380sec w 164K. It seems that this is common with older cars.
Stephen

Sounds like a blower motor to me also, I sell alot of them. 1268200542 complete with fan, or the motor only 0130111001 both avalible right here in the Fastlane catalog http://www.peachparts.com/catalog

Try turning the ignition switch slightly back towards the off position while the engine is running. If the blower comes on, then its just a bad ignition switch.

Good Luck...