Mercedes-Benz 420SEL Door Lock Actuator Replacement Cost

The door lock actuators are a mechanical part that operates every time you lock and unlock the vehicle, so they get used frequently. Due to this frequent use, failure of this item is not uncommon. On some vehicles it's common to have one or more replaced while the car is still under warranty, which can be less than five years old. On other vehicles they can go over 100,000 miles. So it just depends on how much you use the car and what car you drive.

When you have an electronically-controlled door lock actuator that isn't working, the mechanic will need to remove the door panel to verify that it is receiving the appropriate electronic signals to operate the lock motor. If the signals are ok, then the part will need to be replaced. If the signals are not ok, then the issue is with the system that controls the actuator. The mechanic will need to perform an electrical circuit diagnosis to determine why the signal is not reaching the actuator.

To replace this part the mechanic will need to remove the door panel to access the lock actuator mechanism. On some vehicles removal of the window and regulator may be required. If the part is operating a trunk lid or rear hatch on a wagon, the inner panel will need to be removed and the part replaced. When replacing the part it may need to be disconnected from the door lock linkage and electrical wiring, then the new part is reconnected to these items. Once the repair is completed, a thorough performance check of the locking system should be performed to verify a completed repair. This check should include the interior lighting, security system, door windows and any other items attached to the door panel that was removed.

The diagnosis and replacement of the door lock actuator is a fairly straight forward job for an experienced mechanic, so as a consumer it's important that the part is properly diagnosed and replaced. When you get the car returned after the repair, double check that the door panel is secured and fitting correctly. Also make sure all the door locks, interior lights and security system are functioning properly before you leave. If anything is not working be sure to inform the repair shop before you take your car.

This repair, like most repairs on late-model vehicles can be simple or quite complex. Removing a door panel for the first time offers even the most experienced mechanic with challenges as it's easy to break the retaining clips...so when taking this job it's advisable for the amateurs and pros alike to consult a repair manual for door panes instructions. Care needs to be taken when disconnecting and reconnecting any linkages and wiring...go slow and don't force anything. Getting the part out of the door and installing the new one can be challenging because it's very confined and tight inside the door. That said, this repair can be performed by an intermediately experienced person. As with all electronic devices it's crucial they are diagnosed properly or you risk throwing money away on a part that didn't need replacement.