PeachParts Mercedes-Benz Forum

Hello everyone. My 1990 300ce's seat switches have been acting up for a while now. My girlfriend was in the passenger seat and was really tired, so she decided to recline the seat and sleep while I drove. What a great time for the seat switch to quit working.

I researched the issue and realized that it's very common. I went through lots of threads on how to replace or repair them and found useful bits of info scattered around.

Last night I went ahead and tried to clean the passenger side switch, and it worked beautifully. To "repay" this forum, I thought I'd post my step-by-step instructions. Unfortunately I didn't take pics. On monday, I will be cleaning the driver's side switch, so maybe I'll take pics and add them to this thread later. This project took about 1.5-2hrs cuz I went really slowly. That's only for the passenger side. The driver's side should go much faster since I already know what I'm doing this time. I almost bought new switches, but I saved myself around $250 over buying new switches. I'd say it's worth it!!

My 1990 300ce has the memory buttons (i.e. the green dot and the 1 & 2 buttons) on the driver's side, but no memory on the passenger side. Again, I haven't done the drivers' side yet. I'll post instructions for that if they're significantly different that the passenger side (I doubt they will be though).

Tools/stuff needed: Phillips screw driver, Flat-head screw driver, tweezers (optional, but highly recommended), que-tips, and Electrical Contact cleaner. I bought a spray-bottle for $10 at Radioshack. Click here for an example

1) Remove the plastic buttons from the switch on the door (i.e. the little pieces that are meant to look like the seat bottom, back, and headrest). You might have to pull kind of hard. Some people have said they needed to a screwdriver to pry them off, but mine came off somewhat easily by pulling with my two hands. Don't twist or jiggle them- just pull straight back.

2) Where the button for the "seat back" was, you'll see a thick, hollow plastic peg with a little plastic washer around it. It will be the thickest peg sticking out. Remove that little plastic washer (it will be obvious how to do so when you see it).

3) Pry the plastic trim piece that surrounds the switch off of the door. To my memory, there are about 4 spots where it's clipped onto the door. I started at the top left corner and was able to get it off by only using my hands.

4) Now you'll see 2 phillips screws holding the switch unit in place (one on either side). Unscrew them, being very careful not to drop them inside the door.

5) unplug the relays on the back of the switch unit.

6) Don't try to dissassemble the switch while sitting in your car. Go to a table with good lighting and lay down some white paper towels. There are lots of tiny ball bearings and screws inside the switch and it would suck to lose one of them.

7) Unscrew the single phillips screw on the back of the switch. I recommend holding the unit up in the air with the head of the screw pointing straight down towards the ground. This will require you to point the screwdriver toward the ceiling as you unscrew. I say this because if the unit comes apart, everything will stay inside of it.

8) Lay the unit on the table with on it's back... In other words, set it on the side that the screw was in. Iit should still be in one piece, unless it came apart somehow during step #7. Gently pry the thing apart. You'll see multiple plastic clipping mechanisms all around the switch. Un-do these one at a time and it will start to pop open.

9) BE VERY CAREFUL when you pull the cover off. Again, there are lots of little ball bearings that could spill all over the place and you don't want to lose them.

10) Now you'll see another sign of Mercedes engineering genius. Seriously, I was shocked how detailed this little mechanism was. Take your tweezers and carefully pick up each one of the ball bearings that are either rolling around inside the case, or are properly sitting on the tops of the springs. I put them in a little shot glass while I was working to keep them safe.

11) Spend some time examining how the device works. You'll see that it's very logical and there's a system to it. This way, you'll understand how to put it back together.

12) For each of the "pegs" that are sticking up (i.e. the things that the buttons used to be attached to), there should be a total of 4 ball bearings and two springs. This excludes the "peg" that the headrest button goes on-it's a little different. All of the bearings and springs are identical, so don't worry about mixing them up. Since you've already removed the bearings sitting on the springs, remove each of the springs and put them in a safe place. Just grab them with your tweezers and pull them up out of the holes that they're sitting in.

9) Now if you look down the holes that the springs were in, you'll see another ball bearing in each of them. By now, some of them might have rolled out of their oringinal location (mine were all over the place). No prob, just take them out and put them in a safe place.

10) Gently pull each "peg" out of its location. The ball bearings are gonna roll around. Again, just pick them up and put them somewhere safe. Note that the middle peg (it should have a little white, spring-loaded tip) won't need to come out. Leave it there, cuz it's seated pretty firmly in place. You won't need to remove it to clean the contact points.

11) for each of the pegs that you removed, you'll see some "U-shaped" copper-colord metal pieces. These are the culprits of your seat woes. All of these peices are identical. Take your tweezers and pull them out.

12) On the back side of these U-shaped pieces, there will be little bump things at the ends. These are the parts where the electricity is conducted. You'll probably see that they're gunky (which is a good sign cuz you'll be able to clean them!). Take your que-tips, spray one end with the cleaner, and scrub away at these bump thingies. Clean all of them up.

13) Inside the switch housing, you'll see the corresponding contact points where the things you just cleaned usually sit. Clean those contact points as well, using the que-tips. I don't think that's how you spell que-tips, but you know what I'm talking about. ;)

14) When you're done with all of your cleaning, it's time to reassemble. This is pretty easy. Take each of those metal u-shaped things and reinstall them.

15) Install all of the pegs in their original locations (the ball-bearings and springs will come next). If you're confused about where everything goes, use the front piece of the switch unit to guide you. The holes will make it clear how things are arranged.

16) For each "peg unit" drop a bearing in the hole that the spring goes into. One bearing per hole. Then drop a spring into the holes over the bearings.

17) You should have bearings left over at this point. This is the delicate part. Take carefully set a bearing ontop of each spring. Don't bump the table cuz they'll fall off!

18) GENTLY replace the other half of the switch unit. Again, don't jiggle it around, or those balls will fall off the springs and you'll have to put them back!

19) At this point, if it's all clipped down, you should be able to test it by giving it a little shake. If you hear something rattling around in there, a ball bearing got loose and you need open it back up and repeat step 17.

20) Replace the screw holding the two pieces together. Test all of the switches to make sure that they move correctly.

21) Take it out to the car, plug the relays back in, and see if it worked!! If it did, congrats! Put the unit in the door, put the two screws back on, replace the trim piece, replace the little plastic washer, and snap the buttons back on. And there you have it!! Rejoice in the fact that the stealership didn't take you to the cleaners on a part that just needed a little maintenance!

Let me know if you have any questions!! Good luck.

Peter