How do you replace flasher on the side mirror of Mercedes Benz C320?

Hi, it simple, but you would need to be careful not to damage the glass and the mirror frame, all you need to do is:

1: remove the mirror glass, by pulling a metal clip that is locate behind the glass on the top area, you can use and small hook or screwdriver, once you lift the clip you can pull the mirror out toward the back of the vehicle, you are gonna feel that is not loose yet, but it is. it a little bit tricky.

2: remove the mirror frame cover. vent the frame toward the back of the vehicle exposing the inside assembly( is gonna be a little bit hard because of the spring). now you will need a flat head screwdriver to move the clip that holds the mirror cover to the frame, this clip is like aluminum color, most of the parts are black painted,

3: once you have the cover out you will see the two screw (T10) that holds the blinker to the cover.

hope this helps you to get the mirror blinker out,