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R129 Roof and roll bar operation

KenD

New Member
Joined
Dec 3, 2013
Messages
7
Location
Pembrokeshire
Car
Mercedes SL320
First need to post here after 5 years of largely trouble free driving of my 1999 R129 SL320. Anyway here is the problem:
With the roof down I raised the rollbar to remove the wind deflector. The rollbar would not retract. Tried the hold button down to reset but to no avail. Tried to raise the roof - would not work (probably a bad move in retrospect but the car was outside and it was about to rain). Ended up manually raising the roof with the rollbar up.
I still couldn't lower the rollbar so with assistance it was manually lowered. Then tried to lower the roof - the windows opened as normal, but rather than the catches releasing, the rollbar came up, at which point the operation stopped.
The roof switch is not glowing red.
I've subsequently had a Mercedes specialist look at the car, and the only fault that comes up is an open circuit on the rollbar. No fault showing on the roof operation. He's gone away to consult circuit diagrams etc.
I've looked through the forum but can't find a similar problem. I'm hoping my Mercedes man can resolve it but he's admitted he's not seen this problem before. Anyone have any ideas?
 
I've seen it before.

It was a sticky switch at the top of the screen. There are not many roof faults on 129's that I haven't come across. It could be something else also. Try opening the roof again and then erasing the code. See if that works.
 
Thanks for coming back to me. Will certainly try that and see if it works. One question though (and excuse my ignorance) but is there a link between the roof operation and the rollbar? I could understand a sticking switch causing the roof not to open, but why would the attempted operation of the roof cause the rollbar to raise?
 
One question though (and excuse my ignorance) but is there a link between the roof operation and the rollbar?

Yes - the roof, rollbar and front windows are all inter-linked through the roof control module. It will drop the windows (and roll bar, if necessary) when you operate the hood. There's other stuff in there as well e.g. it won't unlatch the hard top unless the doors are open!
 
Sorry for not coming back sooner however my MB man has not been able to get to me for various reasons.
Anyway I will let you know if BlackC55's suggestion works. And thanks Bill for explaining regarding the roof/rollbar operation.
I guess what I still don't get is why I can't lower the roll bar with the switch when the roof is down (manually lowered) or up (manually raised). But I suppose from what has been said something (ie the mentioned switch) is interfering with the roof operation and is therefore preventing the rollbar operation.
 
The slightly odd thing is that you don't have any sensor-related fault codes logged.

I had spurious window sensor errors caused simply by low voltage at startup, and those disabled the roof and roll bar until cleared via STAR. I bought a maintenance charger for the car after that!

Hope you get it sorted - let us know what happens!
 
An update. Have been away for a few weeks but spent some time yesterday with my MB man. In short he has not been able to resolve the issue. The only fault code is an "open circuit" on the rollbar retract operation. He changed the actuator switch on the rollbar itself and the rollbar switch on the dash but that has made no difference - the rollbar will still not retract. If the rollbar is manually retracted then when the switch is used to lower the roof, the sequence of operation is that the windows go down, and the rollbar comes up. At which point it stops and the red roof light goes off. With both the roof and rollbar manually lowered, then using the switch to raise the roof simply causes the rollbar to raise and the sequence then stops. The MB man reckons it is either the ECU or the connection between the ECU and the aforementioned actuator switch. In fairness the guy I am using is not a R129 expert - there are very few R129's around here, so whereas he has the manuals/STAR etc, he does not have the experience.

I guess my next step is to take it to a R129 specialist and see if they can get to the bottom of the problem. Can anyone recommend someone preferably in South Wales?
 
A belated update. On recommendation from this forum I took the car to a MB specialist in Swansea. That was in late May. 3 months later, they have replaced the ECU (long long wait for that from Germany) and some other components. Having been advised earlier this week that the roof was now working properly I had planned to collect the car today (just in time for the end of the Summer!). However earlier today I was told that whereas the roof/roll bar was now working, the lid that should open automatically to allow the roof to be stored doesn't. Apparently when lowering the roof now stops halfway - so in otherwords its not working! A little vague but I have not actually seen the roof operation so I am describing what I was told.

The mechanic/garage owner concerned then added that they didn't actually have a wiring diagram for this model and had to get one TODAY from MB in order to try and isolate and fix the problem - which so far they have not managed to do! So in short they have done all this work on the car without the correct wiring diagram.

Have to say I have totally lost faith in this garage. I'm going to collect the car from them regardless after the Bank Holiday. On their current track record I am guessing they will not have resolved the lid operation.

So if there are any R129 specialists out there who have any thoughts on this then please let me know. Happy to take the car anwhere (within reason) to get this sorted out once and for all.
 
Think a phone call to Olly (Blackc55) at Horndean would be a good move.
 
I have the same problem. Did you ever solve it? I don't want to open anything before I am sure of it.
 

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