2008 Mercedes-Benz ML320 Sunroof Switch Replacement Cost

The sunroof switch is the mechanism behind the buttons pressed by the user in order to cause the power sliding sunroof to lift, lower, slide open or slide closed. It should not be confused with sunroof position switches or any other switch relating the function of the sunroof.

Any common user-controlled automotive switch operates on the same basic premise. When the switch is pressed a circuit is either closed or interrupted, which causes the electronic actuation of the connected system. In this case, pressing the sunroof switch, a multi-directional switch, will actuate the sunroof by energizing an electric motor. Depending on the direction the switch is pressed, the polarity of the sunroof drive motor can be changed to reverse the direction of motion. When the switch is released for the sunroof, the motor will lose power, and the sunroof is stopped. On models with automatic sunroof control, the signal is computerized, and pressing the button will alert the sunroof control module or body control module that the sunroof should move to limit, and the control module will power the motor until input from the sunroof position sensor or switch tells the control module the limit has been reached.

Failure of the sunroof switch will either result in inoperability of the sunroof in one or more types of functions, or the failure of the sunroof to cease functioning. For instance, the sunroof may lift or retract, but not close, leaving the sunroof open at all times, and the vehicle unsecured. Also, models that do not use sunroof position sensors to cancel the action of the sunroof will likely blow the fuse shortly after the sunroof makes it to one of its far parameters. This is because the motor can continue to run, but since it cannot open the sunroof, it will likely draw too high of an amperage for the fuse which provides power. Also, the switch may be visibly damaged, leading to an understanding that it must be replaced.