Convenience Control Module Unit
 

I have a 1991 300CE W124. I have a few items which I think are related to the Convenience Control Module:

1) My driver's (L) window will not go all the way down with the auto-mode stopping about 10cm from fully open (always the same position). If I hold the switch it will go all the way down. It did begin fully opening a few times only to resume not fully opening but now it stops at a different position (but again, now always stopping at this new position). At this stopped position, the auto-mode will not work until the window moves down about another 10-15cm and then will resume auto mode or it will fully open if I hold the switch. Passenger (R) door seems to work fine from the inside. Note: driver's window motor has been replaced before I acquired the car.

2) I discovered the open and close feature with the key. It worked last night after driving the car at the driver's door but not the passenger door. (I didn't try the trunk.) This morning... Nothing at the doors or trunk but appearantly the key must be held in the lock position first. After learning this from another member I tried it and the windows did open and close from the driver's door and trunk. Still nothing from the passenger door. Haven't tried the sunroof but I have read that it gets in the act, too, returning to the pop-up position if that is where was when the car was locked. Don't want to run my battery down for now so I have stopped messing with it.

3) The driver and passenger door window does not open slightly when respective the door is opened and close when the door is closed. I am not completely sure that this is supposed to happen, but that is what I have read. (Other 300CE owners... Do your windows do this?)

4) The passenger door key lock does not seem to arm/disarm the anti-theft alarm system. At least, when I lock with the driver's door, and unlock with the passenger door, it sets off the alarm. Trunk will arm/disarm system.

Question: Is the interior light supossed to illuminate when the car is unlocked? Mine doesn't but seems like it should. (Again, other 300CE or W124 owners... Your cars do this?)

MY thoughts: I think there may be a glitch there somewhere with the passenger door switch at the key/door handle, that is causing the alarm and window issue. (?) Make sense? Can the door switch be accessed without taking the door panel off? Had a member suggest disconnecting the alarm and leaving it disconnected. (Haven't tried it yet. Not sure I want to.) Could the alarm module have some issues? (Less likely, I think)

Any advise, thoughts, comments on these issues or if they are all related is greatly appreciated. Any way to test/recondition the convenience module? From what I have read it may not be completely solid state and my have relays in it. Any sources to get a new or used one reasonalbly priced?

- Window not auto-down completely:
Is the window slow? Try lubing the slides to speed it up (down?). It is also possible that the auto circuit is showing its age and tripping out early.

- Window open/close for door opening:
I haven't had a coupe since '92, can't remember that far back. I don't recall this feature on the C124.

- Inside light: Not on unlock, wish it would, and wish the headlamp switch lit up with the key, ...

- Sunroof opening automatically:
Does it in slide also, close it most of the way with the key, when you come back and unlock/open windows, the sunroof will slide back open.

- Passenger door not operating alarm & auto-windows:
In the doorjamb just aft of the lock assembly, there is a large black cap. Pull this out, the connector for the door lock switch is in this cap, you can unplug and test the switch for continuity there.

I thought maybe an increased resistance caused by a dry/dirty lift mechanism might be fooling the system to think the window has reached the end of it's travel. The window is a bit slower than the other one. This was the case with my BMW's sunroof. A clean and lube of the track resolved the malfuction. Any tips to get the door panel off?

Okay, so appearantly it is not supposed to do that. The window clears the opening and weather stripping without it so that makes sense.

Not too sure where you are talking about. Door jamb on the body or the door? There is only a small, black plug approx 12mm in diameter about halfway down on the rear of the door. Could you clearify? Could you post a picture perhaps?

Do you think that a bad switch or connector is still a possible cause since it still locks/unlocks the doors and trunk? Do the door locks go through the convenience module or anti-theft module? Thanks!

The 12mm black plug you noticed at the rear of the door is the one, pull it directly out, it is about 20mm deep. The connector for the door switch is in this plug, pull it out and you'll see what I mean.

Yes, a bad switch or connection is possible. The locks are actuated by a pressure switch back at the pump, when you push a button down or actuate a key-lock it creates pressure or vacuum and activates the pump's cycle.
The alarm and convenience module are activated separately, by the switch in the key-locks (3), which are cleverly routed through a connector that is accessible through a convenient plug in the rear edge of the door.

As far as removing the door panel, not difficult, but difficult to do without damaging any of the clips holding the panel to the door, which will forever bother you if you break them.
All of the clips are basically hooks facing downward. Sliding the door panel up will disengage them, but if done suddenly can damage them.

Lower the window completely if possible.

The mirror trim panel is first. IIRC the '91 has a manual driver's side mirror. On the forward face of the adjustment lever is a slide, slide it toward the door. With this slid out the lever will pull rearward and off of the mirror assembly.

Next the trim panel. There are two posts into the door frame, and a tab at the bottom. I have a curved screwdriver I use to get as close as possible to the top post and pry gently outward, nearly impossible to do without shearing the post, straight out only. Next post is 1/2 way down, same deal, then tip away from the door and pull upward.

Pull the three seat-cushion shapes from the seat-switch nemogram, pull straight away from the switch. Over the round center one is a plastic C-clip, remove it. Now the plastic bezel over the inner door latch-handle and the switch bezel can be pulled off.

Unscrew the lock button.

At the top of the inner door pull, there is a piece of foam obscuring a 10mm-hex bolt. Remove the bolt.

Remove the two phillips screws at either end of the seat switch and free the seat switch (can be left plugged in and hanging).

Grab the inner door latch-handle, and slide the assembly forward until it can be pulled away from the door. With it away from the door enough for finger access behind it, pull the latch-actuating rod upward and out of the clip in the back of this handle.

At the bottom of the map-pocket is the puddle lamp. Pull the notched end of the puddle lamp downward, remove the lamp and un-plug the wires.

At the rear of the door panel is a C-shaped trim around the latch, remove one phillips screw and slide this trim away and out of the door panel.

The door panel is now free to slide upward, the only impeding element remaining is the felt window-wipe at the top of the panel, it is secured by four metal clips to the door steel and also to the door panel.

I find it best to put some upward pressure on the door panel with the grab-handle, work around the perimeter to ensure it is free. I usually put a little upward pressure on the door with my knee against the handle, and work the top with my fingers to free one end or the other of the wipe at the top. Once this wipe is free, the door panel will slide up 25mm or so and pull away from the door. Do this part gently, you can always take more time, but once a clip is broken, it's broken. I don't mean to scare you on the clips (hooks), there are several, but the ones holding the map pocket and armrest will be missed if broken.

Pull the plastic sheeting down carefully and it'll easily re-install, it's a fairly high-mil poly sheet and IMO easy to remove without tearing.

Re-installation is not too difficult either, I usually hang it on the lock pin and install the lock button first, otherwise it will get trapped under the door panel. If it doesn't seem to fit right, you probably have a clip not hooked.

Wow! Thanks for the panel removal instructions! That will be a big help. I would have been pulling out and for sure would have broken a bunch of the clips! The expletives would have been flying!

Can the clips be replaced if they get broken or are they an integral part of the panel? I'll probably get a few from my Mercedes dealer and have them on hand before I attempt to remove it if they are replacable.

The important ones that I mentioned above, are not replaceable as they are molded into the armrest and door pockets. The ones around the perimeter of the panel itself I believe are simply glued to the door panel and I've heard that they can be ordered, am not sure though.

Really not like the Christmas-Tree clips on most door panels, simply a plastic hook open at the bottom, with a slot large enough for sheet-metal and a lead-in. Once the top edge is free they slide quite nicely.

Update... I replaced the convenience relay with one from a later model. Original part number of 124-820-32-26 has been superceded by part number 202-820-09-26 in the Mercedes-Benz parts system for this application. This is appearantly the same module found in "C" Class vehicles (W202) and later W124s. Auto down works fine 100% of the time now on both windows. This feature is controlled 100% by the module.

Hi,can someone tell me where the module is on a 95 C class and also on my 91 300CE
Thank
Rich

Convenience module (window relay) in located under the left rear seat cushion on the w124s (300CE). Push the red tab at the base of the cushion and it will lift up easily. Probably the same location on the "C" class.

Thank You Hamrt and also MB Shop
Rich:)

same problem where to get part
 

I have a 1993 300E and have the same problem as above. I have searched the part number on the net and can only seem to find used ones on ebay anywhere from $50 to $150??? Not sure I want to trust a used one off of ebay.

anyway, where can I get one and what should the cost be?

also, would this keep the radio from working? the radio went out at the same time.

any and all replies greatly appreciated.

What exactly is the radio doing, just totally dead or in CODE mode on the radio screen?
If it is CODE and now your windows don't go express-down, you maybe had your battery go dead at the same time maybe??
Gilly

Its an after market radio and is totally dead, it may be just a coninsidence it happened at the same time. Battery was fine at the point in time this happened, 8 months ago, but I replaced the battery 3 weeks ago.

The windows work with the key, just not with the control panel in the center console.

The seats move as long as the key is not in the ignition and the doors are open.

Wife drove through a flooded roadway when all this happened.

For reference, I had trouble with my convenience control module last summer. Cleaning the contacts of the respective relay within the module cured the problem. Last week I cleaned the contacts of all 8 relays to preclude any further problems. The contacts has a lot of burn on them.

I just had this problem. Fuse 2 controls these. Mine didn't look bad but was.