Mercedes-Benz has announced that certain vehicles may be affected by a door lock defect that can interfere with how the vehicle detects whether a door is open or closed. While many owners may have only noticed what seemed like minor electrical quirks, the company determined that, under specific conditions, the problem could present a potential safety concern.
What Is the Problem?
The issue involves a microswitch located inside the door lock assembly. Over time, moisture can penetrate the plastic housing surrounding the switch. In certain climates, this moisture can lead to corrosion of the electrical contacts, causing the switch to send incorrect information about the door’s status.
When this happens, the vehicle may behave as though a door is still open or closed when it is not. Early symptoms often appear to be simple convenience issues, including:
- Interior lights remaining on after exiting the vehicle.
- The radio or other electrical accessories continuing to operate unexpectedly.
- Inconsistent door status detection.
Although these symptoms may seem minor, Mercedes-Benz determined that the underlying defect could have broader implications if left unaddressed.
How the Investigation Unfolded
Mercedes-Benz first began receiving reports of unusual door lock behavior between 2021 and 2024. At the time, the reports primarily involved comfort features, such as radios or interior lights remaining on after the driver left the vehicle. Because these incidents did not initially suggest a safety hazard, the manufacturer continued monitoring the situation.
In May 2025, a report from outside the United States prompted engineers to begin a much more detailed technical investigation. Over the following months, Mercedes-Benz reviewed diagnostic data, examined affected vehicles and components, worked closely with its supplier, and conducted extensive laboratory testing.
The investigation ultimately found that corrosion inside the door lock microswitch could develop when vehicles were exposed to prolonged periods of high humidity, elevated temperatures, and condensation. Frequent use of the doors could further increase exposure to these conditions.
Engineers also discovered that the problem was heavily influenced by climate. In drier regions, moisture absorbed by the switch housing can gradually dissipate, reducing the likelihood of corrosion. This helped explain why reports were concentrated in certain environments rather than being evenly distributed worldwide.
What Mercedes-Benz Found
After comparing laboratory testing with field reports, Mercedes-Benz concluded that the issue was not tied to a particular production period but instead to environmental conditions that allow moisture to accumulate over long periods.
By July 2026, the company determined that a potential safety risk could not be ruled out and decided corrective action was necessary for affected vehicles, including those sold throughout the United States.
How Common Is the Issue?
According to Mercedes-Benz, the company received 176 reports in the United States between March 2021 and June 2026 that were related to this door lock defect.
Importantly, those reports involved comfort-function issues, such as electronics remaining on unexpectedly. Mercedes-Benz stated that it was not aware of any rollaway incidents in the United States associated with this defect at the time of its investigation.
What Should Owners Do?
If you have noticed interior lights staying on, the radio continuing to play after exiting the vehicle, or other unusual door-related electrical behavior, your vehicle should be inspected by an authorized Mercedes-Benz dealer as soon as possible.
The Bottom Line
This issue serves as a reminder that even small electronic components can have significant consequences when they fail. What initially appeared to be a simple convenience problem was eventually traced to moisture-related corrosion inside the door lock mechanism. Through years of monitoring, engineering analysis, and environmental testing, Mercedes-Benz determined that the defect warranted corrective action to help ensure the continued safe operation of affected vehicles.
