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Mercedes-Benz E-Class and E-Class AMG: Why is My Power Window Not Working?

Like a lot of things that go wrong with a car, figuring out why your power windows have stopped working is often the most expensive part of getting them fixed. Here's how to diagnose the problem yourself and save some money in the process.

By Craig Steenburgh - June 2, 2015

This article applies to the Mercedes-Benz E-Class and E-Class AMG (2002-2009).

Few things can be more frustrating to diagnose than a problem with your Mercedes-Benz E-Class electrics or electronics. When it's a problem with the power windows on your Benz, it could be any number of things—from a bad fuse to a burned-out window motor and a lot of things in between. Those in-between causes even include a problem with the software that controls the window function—yes, even the windows are computerized. In this article, we talk about how to figure out what's wrong so you arrive at the dealer with some potentially money-saving information—and maybe even avoid the dealership altogether.

Materials Needed

  • None

Step 1 – Determine whether the problem is mechanical or electrical

It's usually fairly obvious if you're dealing with a mechanical problem—when you try to raise or lower the window, it will look and sound like it is trying to move, but it doesn't move more than a fraction of an inch if it moves at all. You may also hear a variety of clunking, grinding and clicking noises. If that's the case, it is almost certainly the window regulator. There's a how-to for replacing the window regulator below.

(Related Article: How to Replace Window Regulator - MBWorld.org)

If the problem is not mechanical, go to Step 2.

Step 2 – Is it just the express up/down that's not working?

If the window still goes up and down but the express open/close feature is not working, it's just a matter of re-synchronizing the windows (and the sunroof as well, if your car has the express feature on the sunroof). This usually happens if the battery has been disconnected for some reason. The synchronization procedure takes only a couple of minutes.

Featured Video: Window and Sunroof Re-Learned

If the window is not working at all, go to Step 3.

Step 3 – Listen for a "click" when you try the window switch

Electrical gremlins are among the toughest to trace, but you can narrow down the possibilities.

Try the window switch and listen for a "click" sound. If you hear a click, it means the switch is okay, and power is getting to the switch. That puts the problem a little further down the line, somewhere between the switch and the motor, or the motor itself may have failed.

If you don't hear the "click," it could mean the switch has failed or that power is not getting to the switch—but there are other reasons you don't hear the "click," so don't starting ripping the door open just yet.

Figure 1. Listen for clicks when using the switch.

If you don't hear a "click" when you try the window switch, go to Step 4.

Step 4 – Try the power seat and power mirror controls

If you didn't hear the "click" when you tried the window switch, the problem could be a number of things—power is not getting to the switch or the switch has failed. It could also be a part called the Door Control Module, or DCM, which manages the functioning of the power window as well as the power seat and power mirror. If the seat and mirror are not working, the problem is almost certainly related to the DCM located inside the door.

As a first step, check the fuse for the DCM. If the fuse is okay, the problem is likely the DCM itself, or it could be that the software for the DCM needs to be updated or refreshed. If you suspect the DCM, insist that the dealership try refreshing or "flashing" the DCM software before they do anything else. This is a fast and inexpensive job and is the subject of a couple of Dealer Service Bulletins issued in 2008.

If that does not correct the window problem, the problem is likely the DCM itself.

  • Figure 2. Passenger side Door Control Module from a 2006 W211.
  • Figure 3. Depending on your model, there could be as many as four DCMs in your car—one in each door.

Pro Tip

Replacing the Door Control Module is a fairly simple operation, and used versions of the part can be found on various on-line auction and buy-and-sell sites.

Featured Video: Door Control Module Replacement

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