UPDATE: Summary – My soft close door locks are really now fixed and working! It can cost you about $15 in parts, but not me….
For a more detailed description of events on how I got my soft close door lock to work, read on.
So, in my last post, I said my soft close doors worked after adjusting the door strike. It worked fine for a few days but then quit again. I found out that if I unplugged and plugged the trunk battery, the soft close feature would work for two cycles and then quit. I also found out if I unplugged and plugged the power harness to the door computer module, the same above situation would occur. This led me to believe that the front door computer module went bad. So, off to the dealership to get a new replacement module. The new door module would cost $195 plus $26 core charge. The module is not new and is a remanufacture. Also after installing the module, it would require a reflash in order to make it work with the car. Needless to say, I decided this would not be the way to go. I then decided that the possible issue is that my existing module is corrupted and needed a reflash. So, I went to my independent Mercedes mechanic and asked him to hook up his STAR Diagnostic computer to my car and reflash the door module. He said mostly likely that would not correct the issue. I asked him to reflash the module anyways. So, he did and then said the module was perfectly fine and there was nothing wrong with it. However, the soft door close feature would still not work. I went home puzzled, minus $150….
The next day, I spoke to my mechanic and he said that since the module is fine, it must be the door lock that is defective. I kind of doubted that, but he explained that when I pull the power to the module, it basically reset itself and the soft close feature would work a couple times and then stop working. The door lock is sending an error to the module and that is why it quit.
A couple of months earlier, I had suspected the door lock itself was defective. I had bought a used one from eBay hoping that replacing the door lock would fix the problem. When I got the used door lock, I realized that Mercedes made that lock as tough as a Chinese puzzle. I gave up cracking apart that door lock unit after staring at it for a couple of hours. I then decided to replace the bad door lock without cracking apart and swap with the eBay door lock. However, getting to the existing door lock itself is a real chore which I put off for a couple of months. (For instructions on how to remove the door lock, see below after this description of events.)
I swapped out the door lock with the eBay replacement lock and immediately my soft close feature worked again! But in the next day, I noticed other different problems have cropped up with the replacement door lock unit. First, when shutting off the engine and opening the door, the dome lights would not turn on, my radio would not turn off, the dash would not turn off and worst of all, I could not lock the doors! I would have to keep fiddling with the door handle till that function would work. On the second day, it got so bad, that when I was far from home, the situation of not having the electrical system shut off and not being able to lock the doors was far worse that the soft close feature not working. At least with my original lock, I just needed to slam the door shut.
That night, I took apart my door again and reinstalled my original lock. The next morning, I resigned to the fact that I would need a new door lock, so it was off to the dealership. They wanted $565 for the new door lock. Ugh! So I ordered it and it would come in a couple of days.
That evening, I decided to try again to crack the #$%!?* Chinese puzzle. After a couple of hours, I was successful! (For instructions on how to break apart the door lock, see the instructions below after this description of events.) It turns out there were three microswitches epoxied inside the off-white plastic housing. These microswitch replacement would be very hard to find….
I had a similar issue on my 2003 Jaguar XJR a few years ago where the door microswitch would fail and the dome light would not turn on. It also did funny things to the alarm system and set it off. It turns out that oil would separate from grease over time and the oil would get inside the microswitch causing failure. Also it did not help that the Jaguar door lock was not covered like the Mercedes version, so all the guts were exposed inside the door, subjecting it to water intrusion. (Cheap Brits!) Fortunately I found the correct microswitch on the Jaguar forums and got replacements. I replaced the microswitches on all four doors, which was way easier than the Mercedes. (Clever Brits!) No more problems!
I dug around the Mercedes forums looking for a microswitch model number, but could not find anything. So the following night in desperation, I searched all over the internet for that Mercedes microswitch. I went back to the website of the company that I had bought my microswitch from for the Jaguar, but they had over 3,000 different microswitches in stock. I randomly looked at the switches and fortunately they had a search by image feature on their website. After scrolling over 20 pages, bingo! I found it! It was manufactured by a German company called Marquardt and it was the 1055 series. However, under the 1055 series, that had another 9 subversions. Which one I had, I did not know. The pins were covered in epoxy.
In my research, I found out that microswitches don’t last forever. They last about 10,000 cycles. So if you on average open/close your car door 3 times a day, doing the math, the mean failure time is roughly 9 years. My Mercedes is 10 years old. However the passenger doors are opened much less frequently (on my car that is) and the microswitches in those doors should last the lifetime of the care, supposedly…
So, going back to the lock unit, I used a Dremel tool, I dug out the old epoxy covering the pins, unsolder the connections and popped out each microswitch. See Figure 4 and 5. You can see, not all 3 switches were the same. Apparently at the driver’s door lock, it has two left and one right microswitches. Also you can see that two of the microswitches, the rubber boot around the plunger is split. Those microswitches did not have a sharp clicky feel, but rather mushy. The oil / grease got inside the switches. However, the non-split switch still felt good.
So, I ordered the replacement microswitches from mouser.com. I bought 8 switches, just in case of possible future work on the other doors. I installed the three new microswitches, tested and reassembled everything back in reverse. All the electrical features of the door lock work now including the soft close feature. Hurray!! BTW, I am an expert at taking apart and reassembling my door now that I can do it in about 1 hour. Also another thing, the dealership never called me back to come pick up my new door lock. Their loss, my gain!
INSTRUCTIONS TO REMOVE THE DOOR LOCK:
INSTRUCTIONS FOR DOOR LOCK DISASSEMBLY AND REPAIR:
- Remove the two T-30 Torx bolts securing the door panel to the door. One is located inside the storage compartment of the armrest towards the rear and the other is located under the armrest around the middle of the door. Both are hidden behind plastic covers that need to be removed first.
- Pop off the tweeter speaker off the door. It hooks into the door frame by the glass, so pull towards the rear first. Let it hang by the wires. Use a soft wedge and remove plastic cover on door panel that accesses the door module.
- Remove the door panel. Use a soft wedge between the panel and the door and gently / carefully pop the fasteners. Lift off the panel from the window sill.
- Disconnect the cable to the door latch handle at the backside of the panel. Do not disconnect the electric flat cables from the panel to the door module yet. Rotate the panel 90 degrees so the cables are still connected to the door module.
- Remove two rubber plugs on the inner aluminum door panel. See Figure 1 below for locations. Power on the car and lower the window about roughly halfway till you see window mounting bolts in the access holes. Power off the car. Unplug the flat electrical cables from the door panel to the door module. Set aside door panel for safe keeping.
- Remove the T-30 Torx window mounting bolts from the two access holes that hold the window to the track. Lift out the side window and store for safe keeping.
- Make sure the power is off on the car. Disconnect all electric cables connectors going into the door module starting with the power cable first, then the remaining wires/cables and disconnect wire connectors that are attached to the module mounting plate and remove them from the mounting plate. See Figure 2. Remove T-30 Torx bolt to module mounting plate and slide forward to remove module.
- Drill out rivet heads securing the inner aluminum door panel to the door using at least 6.5mm drill bit. For locations, see Figure 1. Do not drill rivets all the way through, but just enough to pop off the heads. Do not drill through the inner aluminum door panel. Use a chisel to remove remaining bits. Carefully remove / vacuum shavings.
- Remove end bolt with 14EP socket to the door hold open piston. At other end of the piston, pop off the end from the balljoint with a large screwdriver. Slide the piston out and remove piston rubber boot as well.
- At the end of the door where the latch is located, remove two rubber fasteners and the door latch plastic trim cover. Remove three T-30 Torx bolts holding the lock mechanism to the door. (1 in front, 2 at the side.)
- At the end of the door at about the level of the outside door handle, remove the 1” rubber plug. Insert a T-15 Torx driver and turn counterclockwise till it stops.
- At the outside door handle, pull out the key lock / IR sensor part, when the outside door handle is pulled. Disconnect electrical connector.
- Take outside door handle, slide to rear and angle / lift out. Disconnect electrical connector at the front of the door handle.
- Remove the two plastic door handle seals at both ends of the handle base at the door. Remove two T-20 Torx screws that were under the seal that hold the outside door handle base to the sheet metal door skin.
- Carefully remove the inner aluminum door panel. Pull panel out a bit to clear two mounting pins at the front and rear of the panel. Work the panel forward to clear the door lock and then pull panel up and down to clear the window tracks mounted on the backside of the inner panel out.
- Once the inner door panel is out, access the door lock from the backside of the removed panel. Everything is now exposed. See Figure 3. Unclip the two harnesses for the wires going to the door lock. Disconnect wire connector to the outside door handle base. Unclip the outside door handle base from the top of the door lock.
- Disconnect two wiring connectors to the door lock unit. Remove door lock button and rubber boot. Slide door lock out, carefully working out the door handle cable with the two foam cable dampers with gray rubber boot and the door lock button wire shaft. Once the door lock is out, remove the black plastic cover to the door lock and disconnect cable from outside door handle base to door lock.
- At this point everything is removed. You have the option of installing in a new door lock or continue with the replacement of the door lock microswitches. See instructions below for INSTRUCTIONS FOR DOOR LOCK DISASSEMBLY AND REPAIR:
- To reinstall, do everything back in reverse. One exception is when securing the inner aluminum door panel back into the door, instead of using rivets, drill small pilot holes through the panel and into the door adjacent to the cut rivets. Use #8, 1/2” long stainless steel screws (from Home Depot) to secure the panel to the door. The exception are the two rivets at the door holder base. Those rivets need to be carefully drilled through completely and new screws installed through the old rivets.
- Remove the tiny T-10 Torx screw holding the metal portion of the lock to the white plastic portion.
- Bend back the metal hook plate at there backside so it is straight and will clear the off-white plastic housing.
- At the backside of the lock, on the off-white portion, locate two gear shaft pins that have a split peened ends. Grind those peened ends flat. See Figure 4.
- At the bottom portion of the lock, try to unhook as many of the black hooks off of the off-white plastic housing.
- Using a punch the similar diameter as the ground off pins, hold the door lock in the air and tap on the two pins. Unhook the remaining hooks at the bottom of the door lock. Unhook snaps at the soft close motor housing.
- Keep tapping on the pins till they are almost pushed out. Unhook the clips on the upper portion of the door lock.
- Pull apart the door lock halves. The upper portion has really sticky glue for watersealing, but keep working the separation till the lock is in two halves.
- Set aside the mechanical portion. Work on the off-white portion. On Figure 4, find the three microswitches, using a Dremel tool carefully grind out the epoxy covering to expose the microswitch electrical pins. Desolder and remove microswitches. Clean very carefully the ends of the remaining pins on the off-white housing. See Figure 6.
- You will notice not all microswitches are not the same. For the driver’s side door lock, there are two left switches and one right switch. Not sure what they are on other doors, but probably reversed on the passenger side.
- Go online to mouser.com, it is a US company based in Texas. The exact switches you will need are manufactured by Marquardt, the series is 1055. See Figure 7. The quantity and subversions of the 1055 microswitches you will need are:
2 Left microswitches, 1055.3654: https://www.mouser.com/ProductDetail...IdOU8itcIdo%3D
1 Right microswitch, 1055.2351: https://www.mouser.com/ProductDetail...SVStM8sSYpY%3D
Info on the switches: https://www.alliedelec.com/m/d/88732...37b424652c.pdf
The left switch pins need to be bent straight and trimmed. The right switch is perfect. If you get the correct left one, you have to order a minimum of 1,000 switches! In the selection above, you can have a minimum order of one. Each microswitch cost a little over $2 each.
- Continue by installing the microswitches in the correct position, trim pins as necessary, solder the two pins, test, and then fill the pin tub with epoxy. See Figure 8.
- Reassemble door lock in reverse. First close the latch before assembling to prevent damage to the microswitch plungers. See Figure 5. However, when putting the lock together and just before fully closing, make sure the microswitch for the cam on the soft close portion has the depression of the cam lined up with the plunger of the microswitch, otherwise the cam will sandwich the plunger against the outer body and the switch will be jammed and not work.(I found out the hard way after reinstalling everything. The soft close motor will run four revolutions for it does not know when to stop. Eventually after a couple of cycles of opening and closing the door, the soft close operation will quit. Remember at the top of the post why it runs only two cycles.) It is difficult to see if the plunger has lined up with the cam depression, but looking at it with full sunlight will help. Use a fine pick to depress the plunger of the microswitch to make sure it is in the cam depression and in the correct position.
- Then reinstall door lock onto inner door panel and outside door handle base to door lock. Install the inner door panel assembly per line number 19 in the Remove the Door Lock instructions above.
The last thing is the plug in the power to the door module. Everything should work like the way it supposed to. Good luck!