AWR-fix: Door Lock Actuator Repair

[andrewwynn]

First things first: credit where due; Thanks to @oldskewel for getting the ball rolling on this repair; I didn't want to make a car inoperable to take out an actuator for learning, especially in case i destroyed it, I also didn't want to buy a used one for $50 that would also need the same repair done, again just for learning. To see many more photos of the internal workings of the lock mechanism visit the original repair thread here



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I fixed my wife's 3rd of 4 door actuators today (one more to go). I took detailed photos so I could share and other people can stop spending $100s to replace a $6 motor.



All four of wife's door actuators failed one after the other within about 8 months. Coincidence that her car has automatic lock enabled at about 4mph? Not a chance! Wife's car goes through 2-3x as many lock cycles as my car because of the automatic locking!



Four actuators would be between $600 and $920 at Amazon prices! I've spent $24 so far and will spend another $12 for two more motors: now that I've got the procedure down it only makes sense to replace both primary and secondary lock motors when doing the fix. 96% discount; not bad.







Here's a preview of the actuator just after separation from the latch assembly.







Here's the actuator opened up to show the two motors. The angled one is the double lock motor, the horizontal one is the one most likely to have failed and is the lock motor.



In addition to replacing the door lock motor, I upgraded the latch to be freeze resistant.



I discovered the root cause of all cold weather door handle carrier destruction and created a solution which I will also cover here.



Here is a preview:





The problem is that condensation will form on the latch on a particular joint where a rivet actually touches the bracket that holds it. Look at the photo above; see the shiny spot that is water.



I'm going to post the step by step with captions to my iCloud photos. Tap on a photo to see it full size, tap again to turn captions on/off.



https://www.icloud.com/sharedalbum/#B0SGsCn7Ga0oFm



Just like the design flaw with the siphon jet o-ring, the flaw in the design that kills the door handle carrier is actually the actuator in most cases.



I was completely stunned when I took apart my wife's right front door to fix the actuator motor and by complete coincidence, it was crazy cold outside and was recently above freezing and rainy so even after I brought the car in the garage and even after I removed the actuator it was still frozen solid!



After discovering where the failure point is, I did some testing with drops of water and putting the latch in the freezer. I did about 5 freeze tests and came up with a great solution that is very easy for people to replicate.







Here is a preview of the frost free fix. I applied some low friction material that has double stick tape and then put low temp grease on that too help repel water in the first place.



I put as much water as I could get to stick around the joint and put it in the freezer for almost two hours. After removing I could not even feel the resistance from the ice much less have it stick.



In the first tests, I could not break the joint free by hand, it was quite clear that was the actual source of frozen door handles.



I did some experimenting with the door handle carrier as well and replicated the failure mode and again it is quite clear the problem is when the latch is frozen, the cable will not move and the stress is put on the hinge and causes it to break.



BMW incorrectly determined the porblem was water getting in the cable and redesigned the cable to attempt to eliminate water getting into the cable, but as we all know it didn't help, well now we know why: the latch freezes not the cable : the stuck cable is a symptom not the problem



I developed a method tonight to repair that type of DHC (door handle carrier) failure using a single stainless steel zip tie (28¢). I will be making a separate thread on how to repair a DHC.







Quick preview of that repair. It took hours to figure out a solution that can put up with the abuse of pulling on a frozen latch. It was amazing to see the hinge pull itself right apart in spite of a very solid repair.



In the end, tweaking the stainless zip tie so I could make it go around twice was the winning solution! It's so simple and elegant. It only takes a few minutes to perform the fix, and it's quite a lot stronger than originally designed so I recommend adding the steel zip tie to any NEW DHC as well so it will prevent the failure from ever happening again.