Which model of Mercedes do you have? On the 124, the motor is hidden under the hood underneath the wiper motor. On the 1323, I think you have to remove the dashboard. The motor will be somewhere near the AC evaporator, near the dashboard.

The carbon brushes are not brushes at all, but sticks of solid carbon inside the motor, where they rub around and around the armature, working with the magnetic field to spin the motor.Each brush is held in place by a spring.

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Semibodacious Transmogrifications a Specialty

1990 300D 2.5 Turbo sedan 171K (Rudolf)
1985 300D Turbo TD Wagon 219K (Remuda)

"Time flies like and arrow, yet fruit flies like a banana"
---Marx (Groucho)