Hi Folks,

99 ML 320. Rear door will not lock. (I'm talking about the rear cargo hatch. Not the rear passenger seat door.) If you manually lock it from the inside, it will unlock normally (using either the remote or the console mounted switch). But neither the remote nor the console mounted switch will lock it.

I took the interior panel off and can't see anything electrical or mechanical that is dangling.

I think I need a new rear lock actuator. Could you please confirm and also advise any tips I need to replace it.

Thanks in advance.

Ours failed and when it did, the auto locking feature would trigger a lock, unlock, lock, unlock every time I stopped at a stop sign. Was WAY more than aggrevating.

I had that failure mode too, but it was on the passenger doors. It's commonly called "machine gun locks." Dealer fixed it both times. Once under warranty at 23000 miles and once for free (good will) at 75000 miles.

Are you still under warranty? Even if not, I'd argue hard for the good will repair of this known design defect.

But my current problem is on the rear cargo door and it doesn't lock/unlock/lock/etc like the machine gun lock noise.

the locking mechanism failed because of a broken shaft. You will have to replace the whole locking mechanism on the tailgate. It costs about $70 but 1-2 hours of labor charge. my 98 ml failed a year or so ago. Same thing as you described. can lock manually from inside and unlock with remote, but cannot lock by remote or the console lock button. I still have the parts, if you want to see what it looks like, email me and I can send you a pic and show u what was failed.
I will blame this on MB with a poor design. the shaft is made out of plastic and it is bound to fail at some point due to material fatigue. The other problem is that the shaft pushes the latch to unlock and pulls to lock. When the shaft breaks, it can only perform the unlocking function.

Thank you. You mention 1 to 2 hours labor. Are you referring to dealer labor or is that an estimate of how long it should take an avreage do-it-yourselfer to replace it?

Did you replace your own or did you have the dealer do it? If you did it, any words of wisdom you can share?

I paid the dealer to fix it, just checked the invoice and it was 2 hours labor. At that time I wasn't sure what's wrong and asked the dealer to look at it. The dealer had been pretty good to me. They replace my rusty tailgate, as a good faith, after 5 years of ownership.
There is detail procedure on how to remove the tailgate panel and related stuff. you can do a search on this forum and should be able to find it. The part is called cargo handle assembly, part# 163-740-02-93, you may also need the plastic clips, 007-988-99-78. Once you break open the door panel, some of the clips that hold the panel to the door will be damaged and needed to be replaced.
steve

Thanks, Steve.

I've already had the interior panel off a couple of times and, you're right, some of the clips break.

I'll order the parts and give it a go.

PS: I searched before I posted and didn't find much on this subject.

Replacing the rear latch assembly is a piece of cake. You'll have to pull the trim piece above the license plate and the rear panel (disconnect from D-pillar trim, unscrew the middle latch, pull out and push up). You may as well buy new clips all the way around as the ML ones are pretty much crap. The job shouldn't take you more than an hour if you have even limited DIY experience. Two hours at the dealer seems quite excessive. I know warranty time is definately under an hour.

Also, when reinstalling the rear cover, make sure you hook everything in up top and push down.

Thanks, Phaedrus. Good info. I'll post a follow up to share my experiences.

Sunedog -- I've encountered same problem on our '99 ML for the past few months. Last weekend I made time to fix it. As Supradupe explained, the problem also on mine was a broken actuator shaft. Fortunately, I was able to drill a hole in the short stub that was left and inserted a sheet metal screw with a head that would make the necessary connection to the mechanical locking linkage. I tried to be careful in selecting a screw that was not too long in order to avoid interfering with the solenoid action. Also, I was careful to drill a hole that was large enough to accept the screw without splitting the shaft, yet small enough to provide a tight fit for the screw.

The fix may not last forever but then, neither will I!


Geoff

Follow up: Replaced my rear door latch this weekend. Took me exactly an hour. Everything was reasonably easy to figure out. I did waste a little time by removing the license plate lights (2 screws each) and the license plate while I was looking for the hiddeen screws that held the lock actuator to the inside of the door. You don't need to remove those. The screw heads are covered by the trim plate that goes all the way across above the indentation for the license plate. To get that trim off, remove two screws on the outdise and two 8 mm nuts oon the inside.

I bought my part from Phil at Fastlane. His price was $90 v. my local dealer's price of $130. I won't buy parts again from Dick Dyer Mercedes in Columbia, SC. What a scam operation. Phil was great to work with. I ordered online, he called shortly after to confirm some details, and I had my parts when promised. Thank you, Phil.

Thanks for the great thread. I just completed changing the rear hatch lock.

I have a 99 ML 320 with 40,000 miles and had the same symptoms as described above. I removed the rear panel and sure enough, the plastic piece that connects the actuator to the lock was broken. Got the part from the dealer ($97) and just installed it. Works great.

However, after I was done reassembling everything the liscense plate lights don't work. I checked the bulbs, they are o.k. I tried switching the hot and ground wires, but it still doesn't work. I checked the fuse (F9), looked good, but I changed it anyway, and still nothing.

Anyone have any thoughts about what may have happened and how I can correct it??????

I went to the dealer today to see if they could find the source of my problem. After much searching, they discovered that a small plastic splitter that also seems to kick down the voltage had broken. My best guess is that the flashlight that I had placed in the hatch while changing the lock had hit this splitter.

Thanks Geoff, great idea.
I did the same as Geoff after taking a look at the assembly. The only difference was that I used the largest diameter sheet metal screw that would fit the actuator mechanism. I pre-drilled a hole, started the screw to establish a thread pattern and then cut the screw off so that it didn't extend too far into the plastic plunger.

Total job cost was $22 for 8 plastic chistmas tree connectors (not kidding) to replace those that broke during the removal of the panel. Job took about 1.5 hours with the repair of the plunger.

Ski

Thanks for the response. Just a quick off-topic clarification, you are using some sort of 'xmas tree connector' instead of rather expensive trim panel snaps? Please explain.