124 Cabriolet - who can fix?

Page may contain affiliate links. Please see terms for details.

CabrioDave

Active Member
Joined
Dec 18, 2016
Messages
243
Location
West Midlands, UK
Car
A124 E220 Cabriolet
My 1995 cabriolet roof was working perfectly.

Then (is this relevant?) I took it for some underfloor rust treatment, including welding and under sealing. On the way home, I found that the roof action gets interrupted.

For ease of discussion, the normal stages are:
1. Release catches above windscreen; red light goes on in switch.
2. Push switch backwards.
3. Windows (and if necessary rear head restraints) all lower.
4. Rear bow of hood unlocks.
5. Rear bow rises to vertical.
6. Tonneau (hood compartment) cover raises to vertical.
7. Hood folds back and down, into compartment.
8. Tonneau lowers, and locks.
9. Close windscreen catches.
10. Use main switch (or individuals) to raise the windows.​

1 to 4 are working just fine. 5 begins: the bow begins to move up, but stops after anything between 50 and 200 mm. The tonneau cover then opens up and rises, hitting the roof. Everything stops.

I'm thinking: could be hydraulic failure on whatever cylinder lifts the rear bow, OR failure in the "bow raised" switch circuit. I'm assuming that that circuit detects that the bow is fully up, and THEN allows stage 6 to begin. Since stage 6 is indeed beginning, my thoughts are that the "bow raised" detection is operating too soon. If I read the circuit dagrams right, the "bow raised" switch, when it operates, connects its cable to earth ... so I was hoping to find a cable damaged in the recent floor work, and shorting to the body. So far, I haven't.

Findings so far:
a. Fluid reservoir in the boot is at just above the minimum line.
b. I can lift the bow by hand to the vertical position (VERY stiff - scared to force it) and then everything can continue as normal, until the hood is correctly stowed. Putting the hood back up, everything is normal until the rear bow again tries to raise, to let the tonneau cover fold down. It raises slightly, cover comes down and hits the roof.

I did this a few times, and then it started to object - red light in switch flashing.

I'm getting scared now! Do I continue to try and expose all the workings ... or do I take it to someone who knows what they're doing?:dk:

The car is too old for a dealership to understand it (and I'm too poor, anyway) - but do we know of anyone roof-savvy among the independents?

I'm in the West Midlands, in case that's relevant.
 
Thanks for those. I had dug through and found them, actually - it's just that Mercedes have managed to make all these bits so damned hard to get at!

I was rather hoping someone would know a suitable guru ...
 
Step 2 should be, that you push the soft top up manually by hand at the release latch end of the top before you press the red button.. .

As the power hood on the A124 is not fully automatic...
 
Step 2 should be, that you push the soft top up manually by hand at the release latch end of the top before you press the red button.. .

As the power hood on the A124 is not fully automatic...

Yes indeed. That becomes, by habit, so much part of the "release catches" action, that I forgot to specifically mention it! I have (always) been doing that.
 
Last edited:
If it is a leaky cylinder Do you have any oil driping on the floor just forward of the rear wheel/s. Take a look in the wheel arch when the hood compartment is open - look for oil stains. Seems unlikely as the oil tank is full.

Is the engine running, these take a 100 amp hour battery, most I can get here is 66 and I'll be willing to bet a lot of people won't necessarily have a Genuine battery.

Oil the hinges if things are that stiff, I use chain lube in a can with a straw extension, lube is designed with a carrier that helps the oil get into the fittings.

Check the big fuses under the bonnet on the right front suspension tower area - there is a strip fuse and a couple of others that get forgotten about...
 
Last edited:
Thanks for the responses, chaps.

No leaked fluid seen; battery is a newish 67 Ah (but more importantly high-CCA); under-bonnet fuses are fine; and - as always - I run the engine, just above tickover, when moving the roof.

I think i'm going to have to set aside the time and nerve to strip out the various trim items that hide all the gubbins.
 
http://www.benzworld.org/forums/att...ntrol-synchronization-top-controller-pt-1.pdf

Here's a link to broad schematic on the soft top controller- its behind the trim on the driver's rear side trim below the rear window. I am slightly alarmed by "I took it for some underfloor rust treatment, including welding* and under sealing." in case you have damaged the control unit??

* possible depends on where the welder was arced/ earthed on the body??
 
Last edited:
Hi Graeme

Yes, I wondered about voltage spikes from the welder, as well as the heat of welding. The welding dealt with a couple of holes in the wheelarch, forward of the wheels (typical 124).

The controller itself is not in the well in front of the arch (ie behind the side trims), but under the rear seat, at left hand side, and there's no sign of heat there. There are some wires in both wells, and I was rather hoping one might have got melted - putting an inspection camera down there didn't reveal any such, though it does show where the holes have been cut.

I think I'll have to proceed as follows:
- take out seats and rearside trim (I have found instructions for all that), and inspect better in the wells.
- identify wire from controller to bow-raised switch. Check point in the operation at which that wire becomes earthed.
- remove liner to the hood well (how?) and examine what's in there.

Comments, anyone?
 
The door-lock controller is indeed under the seat - on the right.

Over on the left side is the much bigger control box for the roof.
 
Ok working on that location does it look like this ?
https://www.bba-reman.com/gb/catalogue/detailedproduct.aspx?detailedproduct=896
evidently the early w124 and r129 controllers are the same? **

edit the specific DTC codes for the w124 are to be found on page 66 here http://www.diakom.ru/CARS2/pribor/cs1000/manual/cs1000_mb.pdf
This guy in Canada repairs them- He's posted a couple of very informative videos on faults and testing microswitches

e.g. microswitch sequence table
opening%20closing%20sequence.gif


relays
Switch%20and%20Relay%20Positions%20-%20Opening.jpg

error codes [w124 may be slightly different don't know??
DTC_Error_Codes.jpg


MBCluster - Automotive Electronics
https://youtu.be/8kJAfqLP_xw

[YOUTUBE HD]/8kJAfqLP_xw[/YOUTUBE HD]
 
Last edited:
Ooh, lots for me to study there. Thanks, Graeme.

Busy this week, preparing to take a different car to a Bank Holiday weekend rally (and getting my Skoda fixed where I pranged it ...), but I'll have a go afterwards.

Always something ...
 
with the back lazy u say, when u manually left to 90 degrees to the body everything work as it fold inside trunk and locks up right

what about putting roof up, does the closet unlocks and roof operate correctly locks

have you driven it with roof down is their beeping noise or normal no noise.

u say you check hydro level where u looked and have you tried to refill

have looked either side of the back windows on the back skirt before back wheel by hand and seen if there is hydro residue and this where the piston leak too

if there evidence of leak remove back chair completely screws inside bolster once out take side panel out it is seal u need to break seal and repeat operation two man operation i watch the piston u will see a lazy one and squirting oil clearly and the rubber seal perished, u need good engineering firm who can rubber seal for you cost pennies but u need somebody who knows how to replace it
 
Thak you dinoy.
When the hood is going up, all actiona are correct except the raising of the rear bow - the bow stays only part way up, and the tonneau cover tries to come down, hitting it.
If I assist the hood to go up or down, by manually raising the bow, it all continues and locks correctly and the car drives normally (no flashing or beeping).
I have read the fluid level in the reservoir under the protective cover at the right hand side of the boot.
No sign of leaked fluid so far but I will go ahead and remove the interior side panel trim, as you say.
 
- remove liner to the hood well (how?) and examine what's in there.

Comments, anyone?

Removing the liner is easy. With the rear bow raised and the tonneau cover open, remove the two trim pieces on top of the bulkhead (you'll have removed them already if you've taken the side trims off) and a row of clips around the rear edge then lift out the trim. This is mine a couple of weeks ago:



As for your problem, I'd also be inclined to look for a leak, especially from the rear bow actuators. With your reservoir level at just above minimum, where has the fluid gone? It's a closed system and shouldn't consume fluid.
Not having a puddle under the car is not much of an indication either. I recently had a split in one of the main actuator lines on mine and most of the fluid collected in the sill and the chassis rails as the drains were blocked. I syphoned around a litre out of there with no outward signs of any issues.
 
It's got a rear bow actuator seal / control feeling about it. I missed this before but has somebody been welding near it...?

Moisture collects under where the controller sits, it's good to remove and inspect underneath it like the windscreen wash bottle.
 
Last edited:

Users who are viewing this thread

Back
Top Bottom