1985 Mercedes Benz 300sd heater blower motor

It is quite the operation, if you do not have a manual. I do not think you can do it.

Quite possibly it's the brushes inside the blower motor. A very modest expense and well, not real difficult to do with proper instructions. I recommend you go to www.mercedessource.com and they will sell you the brushes along with instructions for installing them - including photos! You have to take out the carpet on the passenger side, the side panel on the right side, the tray under the dash and then you can see the motor housing. I think it's held in with 4 small screws, unplug the wiring and you're ready to take out the old and put in the new...a bit over simplified, but with words and pix directions, you can do it!
Best wishes,
Tom