Unless you’re driving around in some ‘80s econobox, chances are you have electric door locks in your car. As with anything, these electric locks will eventually wear out, leaving you to use a physical key to unlock the door. The horror!

Alright, so using a physical key to unlock the door isn’t the end of the world, but it is a slight hassle if you’re used to the convenience of electric locks. When a door ceases to lock and unlock at the press of a button, it often means that the door’s lock actuator has given up the ghost.

The lock actuator consists of a small electric motor that drives a gearbox, which in turn locks and unlocks the door. It sounds simple enough, right? While it would be easy to jump to the conclusion that you need to order a new part, the truth is, your broken actuator can often be fixed on the cheap—and by that I mean for free.

We’re going to take a look at the insides of a car door lock actuator, see what is broken, and then fix it up like new.

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Digging It Up

The first thing we need to do is get to the lock actuator mechanism, a procedure that will vary from car to car. In some cars it’s easy to get to, and in others, it’s a real challenge. I would classify the 2011 Hyundai Sonata I’m demonstrating with to be on the more difficult end of spectrum.

Please allow my description on removing the lock actuator from this particular model to serve as a passive warning: the extraction process may very well be the hardest part of the job.

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There are two main steps that will be needed for every vehicle. The first is to disconnect the battery before starting. This is especially crucial on modern vehicles with side airbags. Don’t skip this part, do it.

The second step is to remove the door’s interior panel. Every car has its panels affixed differently, but schematics specific to your vehicle can easily be found through a Google search.

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Image: Harbor Freight

Inexpensive interior trim tools like the ones pictured are helpful for this step, but not required. A slew of plastic clips typically run the outer perimeter of the door panel and must be popped out of place.

There are usually at least three or four hidden screws behind the interior door handle, grab pocket, and door mirror triangle. If the door panel isn’t freeing up, it’s probably because there’s still a hidden screw that hasn’t been removed. Don’t force it!

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Peeling away the door panel.

With the interior panel out of the way, there’s often a secondary panel to be removed. This is a dust protector and sound damping layer. On some cars, it’s simply a glued-in plastic piece of film, and on others it’s a rigid plastic-fiber panel like on this Sonata.

Remember how I said this car was on the more difficult side of the repair scale? That’s because everything going on inside of the door is mounted to this secondary panel. The radio speaker, window limiter, window motor, door lock actuator, and everything in between is bolted to it.

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Woah. That’s a lot going on there.

Before I could take out this secondary panel, I had to loosen or remove everything attached to it. The lock actuator on this car is integrated into the door latch itself, which was the first thing that had to be unbolted. Afterwards, I removed the exterior door handle.

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Next, I had to remove the door glass because the window limiter is attached to the secondary panel; it’s not going anywhere if a window pane is still attached to it. Hopefully you don’t have to remove the door glass from your car—it just makes for extra complexity.

Hey look! The side impact protection beam.

Finally, the secondary panel is removed and the door lock actuator is accessible. The actuator assembly can now be seen attached to the back side of the secondary panel. Notice how the door latch and lock actuator are housed in a single unit.

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With the door lock actuator removed from the secondary panel and placed on the bench, it’s time to dig into why this component has ceased to function.

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Breaking It Down

Right, so we’ve still got to get inside of this lock actuator thing. At this point it becomes increasing clear that the manufacturer of the lock actuator didn’t want you fixing it. It is built like a bank vault and there’s no obvious point of entry. Upon further inspection you’ll find that the exterior casing is made up of two or three parts which are held together with small snap-lock tabs.

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You’ll need to grab a couple of small, flat head screwdrivers and start “unlocking” these tabs, all while you slowly pry apart the casing. You’ll probably end up breaking a couple of tabs (I did - oops!) but that’s alright.

Just make sure there are enough tabs remaining to reassembly the casing. While prying the casing apart, you’ll want to observe how the internal moving parts fit together. Heck, take pictures. These will be extremely useful upon reassembly.

Now we’re talkin’.

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The actuator I’m demonstrating with had a three-part casing. With the cases separated, I was at the meat-and-potatoes of the mechanism. The culprit for a non-functioning lock actuator is usually the electric motor, which is the shiny silver rectangular part with a worm gear on the end of it. It just pops out to allow for a closer inspection.

To verify that the motor truly was the problem, I set up a makeshift test by wiring up a 9 volt battery to the terminals on the motor. Sure enough, the motor didn’t spin—it didn’t even make so much as a noise.

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This little test proved that the motor was definitely the problem with the lock actuator. Now, I’m not going to get into physics behind how these little DC (Direct Current) motors operate. What you need to know is that a part inside of the motor, called the commutator, has gotten dirty and has rendered the motor inoperable. To fix the motor, we need to clean the commutator. The first step to cleaning the commutator is to open the end of the motor. This is accomplished by prying back two tiny metal tabs and popping off the plastic end cap.

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You can see that the commutator has a dark discoloration. This graphite and carbon buildup is caused by the brushes which ride along the commutator as the motor spins. Eventually this buildup will reach a point where electrical conductivity can no longer occur, thus resulting in a motor which no longer works.

To clean the commutator, grab some fine-grit sand paper, wrap it around the commutator, and spin the motor’s armature shaft. It won’t take much sanding to see the commutator’s natural copper color come through. Once you have a nice luster you’ll know that the cleaning work is done.

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And just like that, you’ve fixed the electric motor. Pretty easy, right? Now it’s just a matter of putting it all back together correctly.

First things first, put the motor’s end cap back into place, paying close attention to properly seat the brushes atop the commutator. With the end cap installed, bend the small metal tabs back down. These tabs secure the motor’s end cap to the motor body.

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Plop the motor into the actuator and begin snapping the casings together. Be especially mindful of how all the internal gearbox mechanisms line up. More than likely, you will need to realign one or two levers or slots. They will need to fit together just so. You took pictures during disassembly, right? Good.

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With the lock actuator reassembled, the last thing left to do is to put it in the door and refit the interior panels. Take your time to make sure all electrical connectors are back in place and all screws find their homes. Ensuring everything is returned to its rightful spot will guarantee that you don’t get any new rattles when driving down the road.

Now, reconnect the car’s battery and test out your handiwork! Be amazed at how your electric door lock works again. You no longer have to be seen in public using a physical key to enter your car. What a relief.

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Let’s reflect on how much this little repair cost. Oh, that’s right! It cost nothing. Well, I suppose it cost a few hours of time, but it was a fun few hours. Alright, maybe I’m one of the five people who actually thinks stuff like this is enjoyable.

Either way, a new lock actuator for this Hyundai Sonata would have run around $100, so quite a lot was saved by doing this small fix.

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If you have broken electric door locks, you like saving money, and you’re feeling a bit ambitious, then give this repair a try. Just be warned—you might end up with the confidence to mend a lot more things in the future.