Mercedes-Benz 300SL Door Lock Actuator Replacement Cost

Vehicles equipped with power door locks have a power door lock actuator in each door. The door lock actuator is an electronically controlled motor that automatically locks, or unlocks a door, trunk or rear hatch when the driver or passenger pushes a lock/unlock button on any door panel or remote.

Door lock actuators are most commonly electric motors that control a mechanical linkage operating the door locks. In some vehicles they used a system of vacuum motors, hoses and actuators to operate the lock mechanisms. No matter which system your vehicle has there will be a small computer that operates the actuators. The computer will receive signals to lock or unlock a door from the key remote fob, the key lock in the car door, a button on the dash or door panel, or in some case from a remote unlocking signal from OnStar or similar services.

When the door lock actuator fails you may experience doors that will not lock or unlock properly. The actuator can incorporate a door switch so you may also experience interior lights that stay on when the door is closed and security & alarm systems that malfunction. Before they completely fail, you may hear a groaning noise or other noises from the door as the lock is operating. In some cases, the door lock actuators will continuously cycle, draining the battery.

When a door lock actuator stops functioning it will not have any negative effect on how your vehicle drives, it is safe to drive. However there are a few precautions that should be taken. When driving your car, you will have to manually lock the door with the malfunctioning actuator to avoid the door opening in case the vehicle is in an accident. Also when you park your car you will want to manually lock the door to ensure your items in the vehicle are secure.

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.