2005 E320 Rear Window Problem
 

Hello all. Yesterday I took possession of a 2005 E320 with only 32,500 miles on it. It's a CarFax certified Florida car in great condition and I hope to have it a long time (my last E320-W210, lasted almost 18 years). One slight problem with the new car. It has Keyless Go, which is a pretty cool system. But, the passenger side rear door window keeps going down on its own. It doesn't go down in a smooth motion, but goes down a couple of inches at a time, almost like a jerking motion. Most of the time I can make it go back up from the switch on the driver's door, but it takes multiple attempts. I'm not sure if it's the window regulator (I changes a bunch of those on the 210), or the Keyless Go system. Any thoughts? Thanks.

Maybe an intermittent short in the switch? hitting bumps, etc have any effect on this?

I thought about the switch, but this happens whether the car is in motion or not. The window seems to do this most right after the car is unlocked.

The CAN bus window motors have been known to go bad in general. Mine went bad on my car. Of course it is a different car than yours but they both have CAN bus. The dealer can diagnose it with their computers, but a new regulator out of a junk yard might be cheaper. The fact that your switch only works sometimes suggests a fault with the motor/module (one piece).