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Mercedes-Benz E-Class and E-Class AMG: Why Won't My Interior Light Turn On/Off?

If the interior lights in your Mercedes-Benz E-Class or E-Class AMG no longer work properly, read on to learn what you can do to fix them.

By Charlie Gaston - May 4, 2015

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

You've opened and closed the doors to your Mercedes-Benz E-Class or E-Class AMG, but your interior light still does not work properly. The problem could be a malfunctioning Pneumatic System Equipment (PSE) pump or faulty contact switches in your driver and/or passenger side doors. Here are our top tips for fixing the problem. Let's get started with the easiest fix first and then move on to the more complex solutions.

Materials Needed

  • LED replacements
  • Voltmeter (optional)
  • Phillips screwdriver
  • Flat head screwdriver
  • Needle nose pliers
  • Wrench set
  • Torx screwdriver
  • PSE pump or replacement motor

Step 1 – Check the bulbs

They might be blown.

This is an obvious choice when it comes to troubleshooting an interior light that won't turn on; however, many drivers overlook this step.

  • Unclip or unfasten the cover to access the bulb(s) inside.
  • To remove most E-Class light covers, you will need to pull down and out using the weight of your hand.
  • Replace the old bulbs using an equally comparable high-quality LED bulb(s).
  • LED bulbs provide vibrant color that lasts significantly longer than fluorescent bulbs. Therefore, it's recommended to stick to using LED bulbs in your E-Class.
Figure 1. Light cover location.

Pro Tip

While the cover is off, check to see if there are any problems with the wiring due to corrosion, fraying, or a previous bad soldering application.

Step 2 – Test for continuity in the contact switches

They might be malfunctioning.

If your interior lights won't turn on, or, alternately, fail to turn off after you've closed your door, the most likely culprit is a faulty contact switch. Contact switches are located in the door jamb of driver and passenger side doors, as well as in the trunk of the E-Class.

  • Using a voltmeter, check to see if there is continuity when the switch is pushed in or closed.
  • If you do not own a voltmeter, your dealer can perform the check for you.
  • If the switch is faulty, it will need to be replaced.
  • To complete this repair, remove the door panel.
  • Next, disconnect the wiring harness that connects the switch to the door panel.
  • Attach the new switch to the connectors.
Figure 2. Sample door jamb light switch.

Pro Tip

The switches should be producing 12 volts.

Step 3 – Check your Pneumatic System Equipment (PSE) pump

It might be malfunctioning or burnt-out.

The PSE pump performs several important functions in your Mercedes-Benz E-Class and E-Class AMG, including locking and unlocking the doors to your vehicle's cabin and trunk. If your PSE pump is defective or burnt-out, your interior lights won't work properly. The PSE pump is located under the rear seat next to the car's 12V battery.

  • You have two main options for fixing the problem: You could either replace the motor in the pump or purchase a new or used pump to replace the old pump.
  • A burned out pump would, of course, need to be replaced.
  • Used pumps and motors are available online.
Figure 3. PSE pump.

Pro Tip

To preserve your PSE pump for longer, replace your trunk seal. As well, ensure the vent on the upper right portion under your trunk lid is clear. This will promote proper water drainage during rainfall.

Step 4 – Visit a local Mercedes-Benz dealership

You might have an electrical problem.

If the above tips didn't work for you, visit a local Mercedes-Benz dealership. Your vehicle might have a larger, more complex electrical problem, which isn't recommended to attempt to fix on your own (unless you are experienced and able to do so comfortably).

  • Make a service appointment before arriving.

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