Door Lock Actuator Motor Replacement Tutorial

jerryg2112

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Here is the original and one of the replacement motors that I bought. The motors are readily available on ebay and amazon. The common ones are FC280 22125 and FC280 20150. The dimensions are 18mm x 24mm x 30mm. Shaft diameter is 2mm by 10mm long or 20mm long. The shaft and drive gear have splines. I was not able to find a motor with them in this size and configuration so you will have to add a set screw to the drive gear. The motors are available with a flat side or you can grind your own which is what I did. There are two side plug inserts and two mounting holes 11.5 mm apart by the shaft. The motors I bought had the holes but were not threaded. Tapping them is easy. Make sure to get a motor with holes. I bought Mabuchi motors and not the cheaper imitations. I wanted to make sure that the motors had the torque they are rated for and with chinese counterparts you can’t be sure. If I did the replacement and my locks still worked weakly I wouldn’t know for sure if it was the the replacement motor or the mechanical portion of the actuator. Look for the name on the end cap. Mabuchi is molded into the plastic cap.

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The mounting hole thread size is 2.5mm. I found this by trying testing different screws in the original motor till one threaded in. I don’t know the pitch because it wasn’t listed. The hardware store didn’t have a metric tap that size so I decided to tap it 4-40. I planned on using new screws that size but since the thread was so close to the metric size I was able to use the original screws. The difference in pitch acts like a locking nut. I used a cordless drill to hold the tap since it was too small for the tap handles I have. Just tap deep enough that the threads are cut through so you don’t damage the windings in the motor. I had a forming tap from work so I used it instead of the hardware store tap I purchased. The difference is there are not flutes and sharp teeth for cutting the threads. Instead it rolls the material out of the way. This worked well since the material is soft and there were no metal chips to get into the motor. I suggest grinding the lead cutting edges off your tap so you don’t make any metal chips or a try to keep them out of the motor by magnetizing the tap and using a little grease to catch them.

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For disassembly of the actuator you want to rotate the latch all the way to the closed position. This will position the lever inside so it isn’t touching the microswitch for the door monitor. Now you can take apart the actuator without damaging your door position microswitch.

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Remove the 5 screws shown and separate the assembly into two halves.

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Remove the four torx screws and cover. Be careful not to dislodge any of the gears inside. You want to be able to study their orientation for future reassembly.

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There is a stop under the tan gear. Note the positions of the top white gear when the bottom stop is at it’s limit as shown in these two pictures.

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Note the positions of the top white gear with the bottom stop rotated to its’ other limit position. This is the correct orientation for reassembly.

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There is a tab that fits into a space between the spring ends. Reassemble with the tab in this space.

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Remove the 3 screws shown to remove the motor assembly. The seal inside the electrical connector keeps it from coming apart. Pushing in the middle of the electrical terminal with a screwdriver makes removal much easier.

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I was unable to find a replacement drive gear online so I had to modify the original gear by adding a set screw. The hardware store didn’t have set screws this small so I used screws from old sunglasses. You could also use screws from eyeglass repair kits or order something online. Drill a hole approximately .010 smaller than the diameter of your screw. My screw was about .050 in diameter. With drill bits this small (.040) you are not going to be able to use your drill since the chuck won’t hold something that small. You can use a micro chuck like the one on a dremel tool or you could modify a 1/16 drill bit by spinning it in your drill against a grinding wheel till you deduce the diameter to the right size. This works pretty well although your hole isn’t going to be cut as cleanly due to the fact that the tip of the drill is all web now. Drill deep enough to just chamfer the hole with the larger part of the drill so you can start your screw. I had to grind a little of the teeth back because the head of the screw was hitting them before it was against the shaft. The drive gear is fatter than the gear is drives and so it doesn’t affect anything if you need to do this too. I also used 5 minute JB weld on the inside of the drive gear splines to help lock it on the flat of the shaft and a little on the set screw to keep it from unscrewing.

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If you are getting door ajar messages from a closed door this is a good time to try to address that part of the assembly. The little metal lever can be pulled out and bent with a little more arc for better function.

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Reassemble the door lock actuator in reverse order paying attention to the gear positions as previously mentioned in the beginning steps. I lubed all of the gears with vaseline on the shafts and bores. Don’t lube the teeth. Also lubricate all the moving parts in the mechanical section of the lock assembly with grease or oil. Make sure the lever and slot shown in this picture fit together correctly. Don’t forget to position the latch in the closed position on reassembly so you don’t damage the microswitch.

After reassembly and installation test the actuator for function. Most likely the lock will work backwards since the polarity of the motor is opposite of the original.

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This is easy to fix. Just repin the large female connector in the door. Start by prying gently with a small screwdriver while pulling to remove the red piece. Inside you will see a plastic locking clip. With a micro screwdriver you can pry it back and gently pull the wire out of the back.
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This is the passenger front door connector. The correct wires were the two on the end shown in this picture. Just switch them and plug them back in. They lock in place when fully inserted. The back doors had different colored wires in positions 4 and 12. You can check to make sure you have the right wires by testing for 12 volts when locking and unlocking with switching polarity meaning that your multimeter will show 12 volts positive and then 12 volts negative. Remember that you have to push the unlock button on the fob twice to unlock passenger doors. You can also continuity test for the right wires by using the outer two pins in the door lock actuator connector and the male large connector.
 
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Update. I have two locks that have failed. I can hear the motors running for several seconds and believe that the drive gears are spinning on the shafts. I haven't taken them apart yet to confirm but I am pretty sure this is what is happening. I have a few solutions in mind and will post them if they work out. Anyone wanting to attempt this repair might want to hold off until a better solution for the drive gear is found.
 
I actually just replaced the motors in both front latches a couple days ago, and decided to take a slightly different tack on a couple things - the drive gear attachment being one of them. After drilling the hole for the set screw, I had some hesitation that a set screw through the plastic gear collar would withstand the torque without backing out, especially one of such small size that it would have to be in order to fit where it needed.

I ended up using a steel staple (thicker, staple-gun type) as a type of "key" on the flat side of the now D-shaped motor shaft, and forcing it down through the bore in the gear while on the shaft. Then, I bent the rest of the staple over the gear, and clipped it. Time will tell how it will hold, but I can tell you it took quite a bit of force to get the staple down through the gear, so there is a fair amount of pressure holding it in place. The fit will depend on the size of the staple, how much was filed off the shaft, etc, so keep that in mind.

Picture of gear on the motor shaft with staple-key:
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Would like to give my sincere appreciation to jerryg2112 for beginning this thread - My door latches had started intermittently working one by one, and while I have quite a bit of experience with electronics, motors, and the like, I probably would not have cracked them open and attempted to fix without knowing what was inside and exactly what I was in for. Now, instead of the junkyard or hundreds to purchase a new actuator, I'm able to repair all four at the eye-watering cost of... $9. (plus a few hours of my labor)

I will be doing both of the rear latches today, and will post an update with more pictures and details from my experiences, to supplement the already excellent guide this thread began with.
 
Your key idea is what I was thinking of doing as well except I am going to try using the old shaft as the key. I plan on cutting it off the old motor and filing it flat on one side so the splines will be in half of the gear taking off just enough so it is a tight fit.
 
So I pulled apart one of the failed actuators that I had used the set screw method to repair. The gear had slid off the shaft so the teeth didn't mesh anymore. Below is a picture of the spline drive key idea that I mentioned above.

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I filed the motor shaft flat halfway so it's thickness was .040 . I recommend buying motors with flat shafts so you don't have to spend time doing this. Next I filed down the original motor to .050 thick for a stacked total of .090 . The shaft diameter is just under .079 so the press fit was .010 . It was a really tight fit and I had to put it in the vise to press it on. Next time I will try a little less. It is easier to file the shaft down before you cut it off the motor. I used a dremel with a cutoff wheel to get it close then a diamond file to finish it. I will post an update in the future about it's reliability.
 
I wanted to edit the original post to make some corrections but I can't seem to find the edit option. Maybe too much time has passed since then. Anyway I wanted to mention some things. I don't recommend trying to do this to the drivers door actuator. There is a second microswitch inside the drivers door actuator. It is for the key so the system knows when you physically lock and unlock with the key. The second ribbon is very short and will almost certainly break apon disassembly of the actuator.
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As you can see I found this out the hard way.

In post #6 I said that .090 was a little too tight. I tried less and it wound up slipping. You want a nice tight fit and .090 is good.
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Another closeup
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An update on reliability. The two actuators I fixed with this method are still working well. The third with the set screw is also working well but again I don't recommend that method since I did three that way initially and two failed.
 
Thanks for the update; Same here as far as reliability, all four of mine continue to work great; I have been meaning to add some pictures on how I got the driver's door actuator apart - also found out about the second ribbon cable, but was able to work it out without ripping, and tried to take some pictures to show how I did it - I will try and find some time tonight to update with some further info and pictures
 
Same here as far as reliability, all four of mine continue to work great; I have been meaning to add some pictures on how I got the driver's door actuator apart - also found out about the second ribbon cable, but was able to work it out without ripping, and tried to take some pictures to show how I did it - I will try and find some time tonight to update with some further info and pictures

Glad to hear yours' are still working great and you were able to repair the drivers door too. Your staple method is a nice, simple solution. Nice to have more than one choice.

I could have taken more care when I was taking apart the drivers actuator. Common sense should have told me that the drivers door would be more complicated than the others but I wasn't listening;). I just figured it was being stubborn so I pulled a little harder. The door still works except it doesn't know when it is open. It always thinks it is closed.
 
I could have taken more care when I was taking apart the drivers actuator. Common sense should have told me that the drivers door would be more complicated than the others but I wasn't listening;). I just figured it was being stubborn so I pulled a little harder. The door still works except it doesn't know when it is open. It always thinks it is closed.

I came oh-so-close to doing the exact same thing.. why doesn't this thing want to come off?! ** pulls harder **

So another update on reliability, my driver's side has come loose and whirs without actuating. This isn't exactly all that surprising, as I was in a hurry to finish that particular door that day, and it just came out sort of ugly and didn't fit great. Will be taking that apart soon and seeing if I can't get it any better. All the others still work well, granted the drivers side obviously sees more use, but will continue to report back if anything changes.
 
Update: Passenger door lock failed a while ago. The keyed shaft wasn't tight enough apparently. My solution is a shim stock .010 key as shown in these pictures.
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This is a little tedious. Once the shim is pressed in it acts just like a key like in a keyed motor shaft.
As you can see from the previous posts changing these motors has a high failure rate. I would only recommend going this route if you don't mind spending time tinkering around with these locks since you will likely be readdressing actuators that you have fixed already.
 

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