Will R129 Roof Control Unit (1298200097) Work in an A124 Cabriolet?

[mikeleb]

Hi everyone,

I’m new here and also pretty new to working on these cars, so I really appreciate any help or advice.

I have an A124 Cabriolet and my roof control unit is faulty. I’ve been looking for a replacement, but the correct part (usually 1248204026 or similar) is really expensive and hard to find.

I came across a refurbished roof control unit from an R129 SL (part number 1298200097), and I noticed that the connectors and layout seem pretty similar. Has anyone here ever tried using the R129 unit in an A124 cabriolet? If so, did it work, or are there wiring/programming issues that make them incompatible?

I’d love to hear from anyone who has tried this, or who knows for sure whether it can be done.

Thanks in advance!

 

[BTB 500]

I don't think it would work, unfortunately. The big difference is that the R129's roof is fully automatic (controlled by the module), whereas the A124 has latches that have to be operated manually at the front. The A124 also has four windows to operate / check rather than the R129's two, and two 'roll bars' compared to the R129's one. The roof won't operate if the module thinks there's an issue with any of those.

In fact people have even had problems using an R129 module in another R129. There were a number of changes/differences over the years - obvious things like the windows dropping slightly when opening/closing the doors with the hood up (which early cars didn't do) - but also more subtle technical changes.

 

[mikeleb]

Thanks for the detailed explanation—it makes a lot of sense, especially regarding the differences in automation between the R129 and A124 systems.


Just a quick note though: the A124 is a 2-door cabriolet, not 4-door, so it also has two main side windows . Still, I get your point—the window control and overall logic might be more complex or at least different in how it's managed by the module. actually i need to open and close only i am not looking for other things ...


Appreciate the insight! Definitely sounds like these modules are much more specific than they first appear.

 

[BTB 500]

My point about windows was that the R129 only has the ones in the doors, whereas the A124 also has one behind each door that (AFAIK) the module has to lower/raise too when the roof cycles. I know from personal experience that the slightest thing here will cause the module to lock out the roof - I had a spurious error code for one window generated by low battery voltage during engine start on my R129, and that disabled the roof until I was able to get it erased on STAR.

Can you not get your existing roof module repaired/reconditioned? These are 1980s tech. and shouldn't be too complex - I would hazard a guess that a cracked solder joint (resulting from vibration and temperature cycles over many years) would be the most likely problem, and that's easily fixed. My wife had an old Audi where the aircon control unit died - I figured I had nothing to lose by taking a look myself and found several cracked solder joints on the main PCB which I was able to re-flow ... worked perfectly after that!





Not sure I'd tackle a roof control module myself but there are repair specialists around who might well be able to sort it out.

Anyway good luck, and I hope you manage to get it fixed. I don''t think we have many A124 owners here any more but it may be that someone with direct experience will chime in!

 

[mikeleb]

My point about windows was that the R129 only has the ones in the doors, whereas the A124 also has one behind each door that (AFAIK) the module has to lower/raise too when the roof cycles. I know from personal experience that the slightest thing here will cause the module to lock out the roof - I had a spurious error code for one window generated by low battery voltage during engine start on my R129, and that disabled the roof until I was able to get it erased on STAR.

Can you not get your existing roof module repaired/reconditioned? These are 1980s tech. and shouldn't be too complex - I would hazard a guess that a cracked solder joint (resulting from vibration and temperature cycles over many years) would be the most likely problem, and that's easily fixed. My wife had an old Audi where the aircon control unit died - I figured I had nothing to lose by taking a look myself and found several cracked solder joints on the main PCB which I was able to re-flow ... worked perfectly after that!

View attachment 174050

View attachment 174049

Not sure I'd tackle a roof control module myself but there are repair specialists around who might well be able to sort it out.

Anyway good luck, and I hope you manage to get it fixed. I don''t think we have many A124 owners here any more but it may be that someone with direct experience will chime in!

Great dear .. thanks . my issue is its stolen from my car . i thought it's around 50 to 100$ i disappointed when i checked in Ebay. any way i got already R129 i will try .. and we will see

 

[BTB 500]

my issue is its stolen from my car

Best of luck with getting it sorted. I know the modules are very expensive to replace, that's if you can even find one.

 

[mikeleb]

Best of luck with getting it sorted. I know the modules are very expensive to replace, that's if you can even find one.

i will install R129 it around 100$ here

 

[BTB 500]

I honestly can't see an R129 unit working - pretty sure it will just flag an error on the roof latches when it tries to unlock the hood (if it even gets that far). But if you already have it then nothing to lose by trying.

I suggested repair/recondition because you originally said you had a faulty module:

I have an A124 Cabriolet and my roof control unit is faulty.

 

[mikeleb]

I honestly can't see an R129 unit working - pretty sure it will just flag an error on the roof latches when it tries to unlock the hood (if it even gets that far). But if you already have it then nothing to lose by trying.

I suggested repair/recondition because you originally said you had a faulty module:

i told you the issue , workshop looted from my car. actually there are 2 type of R129 , i will try 1298200097 it has 3 pins . may be you are telling right . but the orders equance same . may be we need some wire hardness

 

[Andy_C]

Hi Mikeleb,
Please could you update this post as to how you get on?
My understanding of the window operation on a 124 is that the roof controller tells the comfort module to raise and lower the windows. On a 129 the roof controller controls the windows itself. This is based on the later (post 95) R129 controller that does not have the separate roll bar controller found on earlier models. I'm unsure of earlier 129 window operation.
If it's of any help in the future, either 124 controller, 124 820 4526 or 124 820 4026 will work in your car. The earlier number, 4026, uses relays to conduct the switching functions, whereas the later module doesn't.
Whilst investigating a problem with my roof controller ( many years ago) I was told that the microcontroller programming between the 129 and 124 modules was different, hence the units not being interchanagble.
I'm sure you've already found the attached, but it may help you if the 129 unit partially works.
Good luck.

 

[mikeleb]

Hi Mikeleb,
Please could you update this post as to how you get on?
My understanding of the window operation on a 124 is that the roof controller tells the comfort module to raise and lower the windows. On a 129 the roof controller controls the windows itself. This is based on the later (post 95) R129 controller that does not have the separate roll bar controller found on earlier models. I'm unsure of earlier 129 window operation.
If it's of any help in the future, either 124 controller, 124 820 4526 or 124 820 4026 will work in your car. The earlier number, 4026, uses relays to conduct the switching functions, whereas the later module doesn't.
Whilst investigating a problem with my roof controller ( many years ago) I was told that the microcontroller programming between the 129 and 124 modules was different, hence the units not being interchanagble.
I'm sure you've already found the attached, but it may help you if the 129 unit partially works.
Good luck.

Thanks for sharing, Andy. Yes, the 129 unit didn't work well, but it did perform some movements. It seems it needs modification. I think the 129 unit for 1996 cars would work better, but the problem is that it only has two ports and doesn't take all the commands.



Yes, there are differences in the commands, but the folding order is the same, regardless of whether it's mechanical or hydraulic. The unit is responsible for the command; the movement is none of its business.

Of course, it's better to use what you mentioned, 124, but I think there are those who are exploiting the price, as 1995 cars are old, but there are very old cars with reasonable unit prices. In general, I'll make some modifications to the 129 and keep you updated.

 

[mikeleb]

Thanks for sharing, Andy. Yes, the 129 unit didn't work well, but it did perform some movements. It seems it needs modification. I think the 129 unit for 1996 cars would work better, but the problem is that it only has two ports and doesn't take all the commands.
View attachment 174264


Yes, there are differences in the commands, but the folding order is the same, regardless of whether it's mechanical or hydraulic. The unit is responsible for the command; the movement is none of its business.

Of course, it's better to use what you mentioned, 124, but I think there are those who are exploiting the price, as 1995 cars are old, but there are very old cars with reasonable unit prices. In general, I'll make some modifications to the 129 and keep you updated.

this 124 three jacks.



but still as a mechanism 129 for 96 models better .. only jack issues

 

[Pontoneer]

Thanks for sharing, Andy. Yes, the 129 unit didn't work well, but it did perform some movements. It seems it needs modification. I think the 129 unit for 1996 cars would work better, but the problem is that it only has two ports and doesn't take all the commands.
View attachment 174264


Yes, there are differences in the commands, but the folding order is the same, regardless of whether it's mechanical or hydraulic. The unit is responsible for the command; the movement is none of its business.

Of course, it's better to use what you mentioned, 124, but I think there are those who are exploiting the price, as 1995 cars are old, but there are very old cars with reasonable unit prices. In general, I'll make some modifications to the 129 and keep you updated.

That unit looks very different to the control module that was under the back seat of my 1993 R129 300SL-24 . Mine was black plastic and assuming the length was the same , was about twice the width of that one .

 

[mikeleb]

That unit looks very different to the control module that was under the back seat of my 1993 R129 300SL-24 . Mine was black plastic and assuming the length was the same , was about twice the width of that one .

yeah, that one different code :0115453832

 

[Andy_C]

yeah, that one different code :0115453832

Hi Mikeleb,
Disappointing but not unexpected.
My understanding was that "early" 129 roof controllers ( 3 plug type) also had a "roll bar controller" whereas the later 2 plug type had the "roll bar controller" incorporated. I'm also led to believe ( only by reading though) that the 129 two plug type of controller will work in any 129 that only has two plugs.
I'm sure you've seen the attachment, but it does look like there is only one connection between the roll bar controller and the roof controller.
If it's of any help, I can tell you that 124 soft top operation is not affected with the rear window regulators removed. I wasn't expecting this result, so I may have an issue with my controller but as it appears to function I'm not going to get concerned.

 

[mikeleb]

Hi Mikeleb,
Disappointing but not unexpected.
My understanding was that "early" 129 roof controllers ( 3 plug type) also had a "roll bar controller" whereas the later 2 plug type had the "roll bar controller" incorporated. I'm also led to believe ( only by reading though) that the 129 two plug type of controller will work in any 129 that only has two plugs.
I'm sure you've seen the attachment, but it does look like there is only one connection between the roll bar controller and the roof controller.
If it's of any help, I can tell you that 124 soft top operation is not affected with the rear window regulators removed. I wasn't expecting this result, so I may have an issue with my controller but as it appears to function I'm not going to get concerned.

i got You . let see after updates what we happen , i will come back to this post . but i didnt understood last attached file

 

[Andy_C]

i got You . let see after updates what we happen , i will come back to this post . but i didnt understood last attached file

Hi Mikeleb,

Last attached file was supposed to show all the components associated with a 124 roof controller. I appreciate its not the easiest to read, but does show, for example that pin 1 of socket X on the controller goes to valve y55y6 ( the soft top open valve) and that socket X pin 11 is connected to earth.
On this attachment (and I'm not 100 per cent certain that this applies to the 129 controller you've got), you can see that it is pin 3 of socket X that goes to y55y6 and that earth is on socket X pin 10.
Apologies if I've caused you confusion.

 

[mikeleb]

Hi Mikeleb,

Last attached file was supposed to show all the components associated with a 124 roof controller. I appreciate its not the easiest to read, but does show, for example that pin 1 of socket X on the controller goes to valve y55y6 ( the soft top open valve) and that socket X pin 11 is connected to earth.
On this attachment (and I'm not 100 per cent certain that this applies to the 129 controller you've got), you can see that it is pin 3 of socket X that goes to y55y6 and that earth is on socket X pin 10.
Apologies if I've caused you confusion.

thanks Me. Andy c , actually i liked the file , I will printed to understand it . appreciate /