Hi,
I have a problem with windows and sunroof not working in my 1990 w124 300d.(I live in the UK so the car is right hand drive non turbo)

They failed on saturday so once home I came onto the forum to do a search and came across a post by Pselphid and had a read through but nothing in the post seemed to scream out a fix to me,Below is a link to the post.

New old 300d and none of the windows go down.


Now on mine at first the sunroof which I had used on tilt and then closed refused to tilt or open about half an hour later when I tried to use it,the drivers window still worked for around the next hour or so until I closed it.

After the drivers window failed to work I tried all the others and they also refused to work.

Upon getting to my destination I inspected the fuses and all were ok,no corrosion neither.

With the drivers door open and key out of the ignition nothing

Door shut and ignition on nothing


Drivers door open and pressing the door switch in and out a relay can be heard to click,this relay is inside the same box as the wiper relay


I have not had the cover off the box and checked out which relay as I have not had the time to do it,I left the car at my fathers and used his van all weekend for mx.

Now when sitting in the car and ignition on or off and with the drivers door either open or closed,there is each time the window or sunroof switches are pressed a distinct audible muted click from under the rear seat.

Is there anything under there ? that has anything to do with the window/sunroof circuit ? that I can check out to narrow the search for the fault down.

All other electrics on the car work as they should,I did think there maybe a thermal fuse somewhere that has fried ?,but I do not know if the car has one as standard.

Does anyone have any ideas ?

There's a Convenience control relay Under the opposite side of the rear seat
from the Door Lock Pump.(It's on the Port side,over here)

The Convenience control feature allows you to roll up the windows/close the
"S" Roof with the key @Driver's door ,Passenger door and the trunk.

This is all just the first thought out of the box...let me cogitate a while on it.

This is the service manual,with wiring diagrams,Etc:
http://www.ps2cho.net/downloads/MB%20CD/W124/Main.html

Also the Damn fuses seem designed to Deceive,they corrode at the Pinch points
but since they're whitish already you can't tell!
Also they develop invisible cracks in the metal.
Looking at them ain't gonna do it.
Testing for continuity with a multimeter is also deceptive...
they need to be tested with a load on!!!

I just bought recently Two new sets of ceramic fuses with Copper metal
and threw all the old ones away.

'Cleaning the fuse holders,be careful you want a smooth gripping surface
not scratched.

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'84 300SD sold
124.128

Thanks

I will chase this relay up.

All the fuses are super clean,and I forgot to mention in my first post that the windows will not work up or down with key in drivers door.

The muted click from under the rear seat must be the Convenience control relay working but with no power coming out,so I will have the seat up and check it out.

I will replace the fuses and clean the fuse terminals before venturing under the seat.

I have just had a thought that I will check the battery connection as well for smaller live wires branching off the main live or a connection near the battery for corrosion because unless this relay is faulty then there is no live power getting to it.

Thanks again.

Circuits:
ATA (Alarm)
Central Locking System
Power Windows
Sliding/Pop-Up Roof

Well you've got Two out of Four..."P" Windows and "S"Roof on the Fritz

(I'm trying to eliminate the CC module [part # 202 820 09 26]...
Cost: [Sit Down,Put Oxygen mask on] $458.00 USD)
[Recycler's/Salvage here I come]

Does the Central Locking System Pump under the Starboard side rear seat
Lock/Unlock the Doors/Trunk/Fuel Door?
(If the CLS works there 's a chance the problem lies elsewhere than the CC unit)

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'84 300SD sold
124.128

Yes all the doors / trunk / fuel door all lock/unlock and work perfectly.


Where I am in the Uk I have quite a few breakers around and one guy in the next village has about 6 or 7 w124s although all gassers he is breaking or exporting to Africa and even a 4matic as well,so I just need to identify what has gone bad and give him a ring and pop down and get the part I need for the cost of a drink.

Over here people view these old Mercs as simply an old car waiting to go wrong and cost a fortune to repair so they can be picked up cheap.

He buys from salvage auctions and as above they go for export to Africa,the Africans will only buy German or Japanese ,they will not touch any other make of car.As long as the car drives and stops then things like windows and other luxuries do not matter.They buy stuff like complete axles etc and fill a container and ship it out.

The rest of his business is collecting and weighing in scrap metal.

I cannot get down there to the weekend but if it appears to be the Convenience control relay I will just replace it and see what happens.

I have checked the system over and there is no power to the relay under the rear seat.
The car has a laserline alarm fitted,I have no remote for the alarm so since owning the car it has not been used.
Removing and replacing fuses see the alarm re boot.
So I have the key to turn the alarm system off,doing so see's the starter engage and turn engine over.
Teasing the key around with out going full turn lets engine run and normal functions.
So I unplug the key barrel from the alarm and although alarm l.e.d stays on everything is working ok.
Now with door closed and no ignition I have the muted click from rear under seat relay.
My problem is either a bad earth or alarm related wiring or earth fault.
This is knocking out the live feed to the under seat relay.
The alarm unit hidden behind glove box has at least 30 wires coming out of it,so hopefully cleaning earthing points may be a cure.

In any of these scenarios ,do you get functioning Windows/Sunroof ?

I'd be Really,Really,Really tempted to REMOVE the Offending Aftermarket
Alarm (And All of it's "Tentacles"/Wiring)
[Almost a rule of thumb...First thing to go... is/are any aftermarket "Hacks".
Howeveah, If you like it (And you seem perfectly capable of Diagnosing
it's "ills") AND you can find a Remote online, you may elect to live with it.]

IF the Problem is NOT the Aftermarket,look into Mercedes Ignition Switch
info below:

When you say "Teasing the Key" are you speaking of your Mercedes Ignition Key?
The electrical part of the Ignition Switch is on the portion of the Locking
Mechanism away from you as you sit in the car.They can sometimes go bad
(Age).
Pictures of electrical Switch and Locking Mechanism:
(The upper of the first two pictures shows the mating surface for the Electrical
part of the system..."See" the three screw holes? This would be facing the
engine compartment,away from you.)(The lower parts of the pictures shows
the "Business End" of the Mechanism.that's where the "Ignition Tumbler" fits in.)

The Third picture is of the Electrical portion of the Ignition ,which mates with
the top portion of the first two pictures.'Forth picture is the Electrical portion
of the Switch (Which faces away from you and receives the PLUG from the
wiring harness.

W124 user friendly service manual online:
http://www.ps2cho.net/downloads/MB%20CD/W124/Main.html

Excellent reference/advice forum in the U.K. :
http://www.mbclub.co.uk/forums/
(helpful,knowledgeable mates)

Thank You for adding to our collective information source,
please keep us "in the loop"!

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'84 300SD sold
124.128

I was teasing the key in the alarm shut off.

If I turned it back to where it was armed I could remove the key halfway out and then turn the lock assembly halfway between off and on,in this position the car would run as normal .


Another update,came back to the car this afternoon,got in and shut the door and started up and drove about 20 yards and sat waiting with the engine running for my son to come out and get in the car,pressed window button and window opened,checked the rest and the sunroof and they all worked.

Now there was no joy this morning and the car has sat most of the day untouched so my theory of bad earth does seem distant now.

Your pictures of the electrical portion of the ignition has me now thinking either that part is worn out or the mechanism is tired and bad internal contact is the order off the day.

Cannot quite get my head around why it would not work as normal with no ignition and either front door open,unless they both interfere with the working of each other ??,so it is time to take the dash apart and have a good look at the alarm wiring and the ignition key electrics.

It's Key operated Switch has proven itself randomly inoperable...
There is No "Random" Pathway for Electrons.
ERGO,Problems =s Anomalous Dis-functional Aftermarket Alarm.
Problem IS the Alarm's "Shorts", Whether Bad Install,Bad Alarm Itself or Grounds.

At the very least you'd not be fighting two different systems with
the Alarm out of the picture.You know ZOMEZING is wrong with it.

IF the Alarm is mounted behind the Dash ,you'll do what you have to...
Removing the Instrument Panel is no big deal,it just pulls out
(After you loosen a clamp on the Speedometer cable in the footwell
to give yourself more room to unscrew the cable from the back I P.)

Mercedes Ground(s) are subject to benefit from "Clean and Bright"
There is a grounding point for the Instrument Cluster behind the I.C.



I'm betting the Alarm is the Culprit.
The Windows/Sunroof CANNOT operate independently/without the Comfort
Control Relay...AND you've already proven the Damn Alarm is keeping the
CC relay from getting needed Voltage,At Times.

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'84 300SD sold
124.128

Yes the alarm is going to have to come out.

When it is armed I lose glow plugs and starter motor,I would expect that the auto trans switch and a host of other things are disabled simply by the amount of wires from the alarm unit.

Luckily these are all colour coded so it should just be a case of following them to their destination and removing them and effecting a rejoin on existing wires.

Of the 3 fuses in a block hiding underneath the main fuse box (2 fuses for flashers/one for each side and another which is most likely fuse for the separate alarm siren were all soldered connections where the joins had been made.

If once I am in the dash and all appear to be good soldered connections then I will most likely retrace back to the alarm and just remove the wires there and rejoin them and mark their functions down to enable me to refit another alarm later on.

The ignition barrel will receive a new electrical portion as a matter of course,no good messing around with these,as it is maybe as old as the car at twenty years and this is one fire maybe waiting to happen that I will not be able to put out.

I'd wait and see if removal of the alarm solves the problem.

The "Tumbler" (a Misnomer , on Mercedes it's actually little machined "Leaves"of metal.) is usually the part to go bad...
Throwing that one Lb.bolt and retracting it with each ignition cycle wears it out. Steel MB keys ONLY.
The lesser metal keys output metallic residue ,which hastens the demise of the "Tumbler".

Enjoy.

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'84 300SD sold
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If You're gonna keep this Mercedes...
A "Self Made Version" of Bosch's WR 1 Starter relay ,
shortens the electrical pathway for Current to the Starter Solenoid and prevents overload of the Ignition Switch Component.

The Power doesn't have to travel ALL THE WAY up to the Ignition Switch...
It just jumps through the relay from one starter terminal to another.

The reason I'd wire up my own relay ,is that the Bosch sometimes doesn't
have the relay with a diode across the Magnetic "Pull In" part of the relay
and when the Switch releases the relay EMP can reach 200 volts backflashed
to the Ignition Switch Contacts.And I want to use AWG 10 wire on the High side.

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'84 300SD sold
124.128