I've a 3 day wait to receive more parts from Pelican. A few months ago my two front windows quit working at the same time, no problems before. Around that time I was pulling and reinstalling my original radio to troubleshoot a speaker problem. Got that fixed and didn't notice the windows until some time later.

Rears work fine

Questions: From the wiring diagram it appears to be the comfort module has failed. For those of you familiar with this module and wiring, is it the most likely cause?

Do you know if the wiring from the switches goes to the area beneath the radio? There are quite a few wires jumbled up there.

I believe the comfort module part # is 202 820 09 26

Another member had issues with the comfort module causing window problems not too terribly long ago. Like most electronic modules in these cars, the most likely cause of issues is poor solder joints in the module.

You can test the switches by swapping wiring between a window that works and one that doesn't. If the problem follows the switch, you know the switch is bad. If the problem stays with the window, it could easily be the comfort module.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Thanks Diseasel300

I have no sound or movement for either front window while engaging their switch.

Found a wiring diagram from the Russian site and looks like the ground level from the chassis is switched to the comfort/convenience control unit.

Also found a couple of comments about repair of the module by removing plastic cover and cleaning the relay contacts with fine sandpaper and contact cleaner spray. I don't really believe cleaning will fix my problem since both operate separately and failed at same time. I'll do the cleaning anyway though just to make sure.

Supposedly can activate window action by manually engaging relay ( one comment ).

I'll also look up my wire tracing gizmo I've used for house electrical and signal wiring. Also have an old Tektronix synchroscope that might come in handy ( if it still works ).

Hoping it is a connection knocked loose while fiddling with the radio. Will let y'all know what I find. Finally warming up here in north Texas, got down to 8 degrees one morning. In the 40's now so will make an effort to expose switches and comfort module.

There are a ton of grounds fastened to a single post inside the center console area behind the radio. They're notorious for having poor connections after many years. If you have any switched ground going to that area and you were playing in that area recently, that would be my very first suspect. Could be a loose connection, or a wire that broke off of an eyelet.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Learned another upsetting lesson. I'll try to explain it so a few might avoid doing something similar.

Basically, two 10mm nuts hold the module in place, easy to remove.
2. Middle 3 wires easy to remove
3. Two remaining big plugs with about 12 wires each wouldn't budge, tried looking up how to remove by searching forums and internet. No help found. Finally decided to remove small black section on each plug that has wavy openings. Pulled on plugs and all the wires came loose. Plastic plug stayed without moving.

Took the comfort module inside where it was warm and good like to figure it out.

What I should have done was push a raised tab about 3/4" to the inside from the wires. This would have popped the plugs out with the wires attached properly.

One picture shows both connectors installed in the comfort module, the small screw driver handle points to the tab for the left connector. You should notice that you can't push on those until you remove the middle 3 small connectors. This will allow the left connector to pop out when you push it's tab. Push the right connectors tab to remove that one. Of course this has to be done while still installed in the car because the wires are supposed to stay in those two connectors.

Other pictures show circuit board, inside relays and points, front window relays show more wear. Yellow pieces show inside retainer positions that must be released to remove cover. Other case pictures show those inside retainers.

Attached Thumbnails

         

More pictures, release tabs for cover, internal circuit board with the 8 relays for window control activated by manual switches inside or key action from driver side door, a few relay points

Points show some wear from front window control. Rear window relay points show minimal wear. I've been reading on how to clean relay points. Supposedly any rubbing will wear them a little more, but will smooth out the surface and possibly remove some corrosion from arcing. Some sites said cleaning by rubbing will reduce point life. Other said to use really fine garnett body shop 2000 grit or higher to reduce chance of embedding sanding particles.

I'll probably buy a small burnishing tool and use contact spray.

Guessing I'll have to remove door panels to make sure front window motors are in good shape. Window slides could use a good cleaning and lube anyway.

Don't like the idea of breaking panel mounting or plastic parts. Have searched for how to remove panels for 95 W125 E300D, found mention it is slightly different than years before - but nothing in detail.

Will post new thread asking how to remove door panels and inside wood finished trim where window switches are mounted. No screws or releases are visible.

Attached Thumbnails

         

Luckily the wires were much easier to get back in place ( once I figured out how ).

Basically, the small plastic slide ( U shaped with waves, just beneath the top of the plug ) needs to be pulled out about 3/8" so the plastic holding the wires can be put into position and bottomed out.

Then the small plastic slide is pushed back in and it will grab two little plastic dots on each side of the plastic holding the wires. This locks the plastic holding the wires in place.

The big plugs are marked A and B and will only install into the respective position on the comfort module. The two little slides are the same part #.

After working with it enough to understand it:
I like the design of the plugs
the wire size and connectors are good,
it is easy to clean,
I like that the window switches do not carry high current, they switch a ground signal that goes to the comfort module circuit board. Would be better if the switches were easy to remove for spray cleaning every few years.

Main change I would have made is to have the relays individually replaceable without soldering. Possibly slightly bigger contacts but if your window slides are properly lubed the size is probably adequate.

Also If all windows are energized via the door switch and go up or down at the same time, it seems that could cause a very high current load to be handled by the module. Due to this I probably won't be using the door switch.

Looking over the window control wiring diagram again I noticed that there is a relay located under the engine area fuse box that funnels two 25 amp lines to the comfort module. Makes sense that each of these probably supports two windows each. One of the contacts could also be my problem. Once life quits getting in my way I'll spend more time on my window problem. Changed a tie rod ball joint yesterday, driver's side motor mount today and temporary re-install of intake manifold so I can move the car out of rain expected this weekend. Still not waterproof due to wiper assembly being removed for pull apart and lubing.

Finally got back to working on my car a couple of weeks ago. Recently replaced the convenience relay located beneath the fuse panel that provides voltage to the window control board installed beneath the passenger seat. I also cleaned the contacts on that control board with spray contact cleaner. The tiny relay points didn't look too corroded so I never attempted to burnish them.

After cleaning and with the new relay installed, I tried to test the windows with jumper wires from a spare 12 volt battery. At first the windows would 'click' but not move. I measured the voltage on the battery and it was 11 volts. After a complete charge of the spare battery both front windows moved up and down. I connected that battery to the wires that go to the front windows.

I put the window control board back in it's housing and plugged all the connectors in place. All windows worked from the window switches.

After reviewing the wiring and control relays and fuses, it appears that the single convenience relay beneath the fuse panel can have a load approaching 50 amps if all four windows are engaged from the drivers side door switch. Two 25 amp fuses feed through this relay. This seems excessive if used fairly often. Due to this, I'll try to only engage one window at a time from the interior switches and hopefully reduce the load on that relay to minimal.