Broken door lock project

[natejgreene9871]

I’ve owned my car for almost a year now and the drivers door lock has never worked.

Symptoms:
Tumbler and key would only turn one direction (unlock) position.

If you locked the car from the passenger door, the drivers indicator pin would go down and act like the door locked, but it would not actually lock.

Turns out I had two issues going on.

First issue was the tumbler assembly itself.

Upon removal from the car, key would still only turn in one direction.



I further disassembled the lock by pulling the cylinder out.



The internals were just plain worn out. The inside of the lock housing had deep gouges worn away, the wafers were no longer smooth. The whole thing needed to be replaced. Unfortunately the dealer no longer sells replacement locks or door tumblers.

My options were:

• rekey the whole car (both doors, trunk, glovebox) with a good used set from eBay. pain in ass and expensive.
• Sacrifice the passenger door and swap the driver and passenger door locks- this seemed good at first but I noticed the locks were clearly marked “left” and “right” Turns out they are almost the same and would have worked but the “window” was oriented in the opposite position. I suspect if this opening was pointed up to the sky it could collect water and ice up. See the right vs left key assembly and orientation of hole

I didn’t like either option so I purchased a used left door lock on eBay (with key) and rekeyed it to my car. It was very tedious but I was successful.




I set the eBay donor tumbler and the original tumbler side by side and swapped each wafer and spring one by one. Some springs were broken so I used the best parts between the two. Only about half of the wafers needed to be swapped, the others were the same on both tumblers.



Notice that each wafer has a number, looks like the dealer has a set of wafers and inserts the correct numbers depending on VIN

The name of the game here is to get all of the wafers flush when you insert the key.



You have to be careful and hold the wafers in with your fingers. They are spring loaded and when you pull the key out they want to fly away. Very small be careful

Each wafer had to be carefully removed, cleaned, sanded, and polished to get a nice smooth turning lock. Sanding also helps account for some of the wear on the key itself. I also polished the whole barrel itself.



Carefully check with your fingernail you want the wafers to be as flush as possible. Any that are protruding need to be pulled back out and sanded some more until flush. This was an iterative process with trial and error until things were turning smoothly.

Between the donor and original I was able to cobble together one working lock assembly. Cleaned with rubbing alcohol and assembled with lithium grease

 

[natejgreene9871]

Next up was the door latch itself. This was also broken! Surprisingly frustrating to remove.


The hardest part here is this damn white plastic cover. I don’t know what its purpose is but it is very hard to deal with. I had to basically just yank it out along with the latch.

The latch wraps around this plastic thing and there is just not enough room to maneuver it out easily. I don’t know if there is some kind of trick, I searched online and could find little reference to this.

It took about 45 minutes to remove and and hour and a half to reinstall. I considered just leaving it out, but I’m sure it’s there for a reason. You will need a lot of patience…I ended up cracking mine and had to glue. I suspect it shields water away from the lock.



With the latch removed I carefully inspected it. Some of the little arms inside looked bent and I tried straightening them. It still seemed like something was screwed up internally and given the difficulty of removal I bought a new one.

Was still available at dealer thankfully.


Moderator edit: The driver door latch assembly is p/n 124-720-09-35, MSRP is $208 as of May 2024. Sample dealer here.

 

[natejgreene9871]

Some other thoughts here:

• I bought a full w124 wafer set on alibaba, I’m curious to see when it arrives if it has everything I need to rekey a lock. I will report back.
• I’d love to try and do this with ignition cylinders as well. I’m going to do some experimenting on this.

I have purchased a remote unlock key fob kit I plan to install. It was $30 on eBay. I successfully installed one on my 190e which also suffered a door tumbler failure. Hopefully the w124 wiring will be similar.
You might consider this if you want to preserve the life of your door lock, my car only has 140k miles. The door lock on my w201 failed around 180k miles. Seems somewhat common

 

[doolar]

Some other thoughts here:

• I bought a full w124 wafer set on alibaba, I’m curious to see when it arrives if it has everything I need to rekey a lock. I will report back.
• I’d love to try and do this with ignition cylinders as well. I’m going to do some experimenting on this.

I have purchased a remote unlock key fob kit I plan to install. It was $30 on eBay. I successfully installed one on my 190e which also suffered a door tumbler failure. Hopefully the w124 wiring will be similar.
You might consider this if you want to preserve the life of your door lock, my car only has 140k miles. The door lock on my w201 failed around 180k miles. Seems somewhat common

That is a great idea! With a combination of keeping the lock cylinders clean, lubed and used every now and then they'll probably last forever.

I just use the key, but I try to alternate, using both the trunk lock and passenger side lock often, thus spreading out the wear over three locks.