R129 1990 500SL Computer reset - Roll Bar
 

Hi Everyone,
We own a 1990 R129 500SL Mercedes.

A couple of weeks ago, we took it into the local mechanics shop to have it serviced. Whilst it was in the mechanics, the mechanic made the mistake of starting the vehicle with the wiring loom for the roll bar + roof sensors disconnected.

As a result of that happening, the car has gone into a protect mode, with the roll bar up, and none of the roof functions working. (we can not put the hard top back on, nor automatically put up the soft top.)

I have come to the conclusion that it is a computer issue with the cars body control module (or whatever it is called in mercedes speak :-) ).

As it stands, we have two options, try to fix the issue, or travel a 745 mile round trip to the nearest city to have it serviced. (Yes we are in Australia!).

What I would like to know is if anyone has any ideas on how to reset the computer, as to regain the functions that were detected as malfunctioning, or knows what the cause of the malfunction could be. I would really like to fix this myself, as I don't fancy a 745 mile trip for what could potentially only be a 2minute quick fix!

EDIT: Have had more of a search, and have come across some information that suggests that if an issue is detected with the softtop/roof mechanism, the roll bar is automatically engaged.

What I want to know is once the roll bar is engaged, how do you reset it so that the roof will function again?

Many Thanks
Simon

Resetting the roll bar./
 

hit the roll bar switch to the up position and hold it there until you hear a "click".. then it will be fine..

Hmm, have tried that several times, however have had no luck there.

One thing I forgot to mention is that there are no indicator lights on the roll bar switch. This could be an electrical falut, however I have checked every fuse in the car and they are all fine....

Hit the roll bar switch into the down position for 20 seconds.. then try the up position for 10..

If that doesn't work check the fuse.. It could have tripped.. Also try wiggling the rollbar.. give it a slight whack towards the down position with your hand.. Something may have jammed in the mechanism..

Just my .02

Good Luck.

You probably need to read and clear codes on the soft top controller and roll bar controller. The procedure was explained here: https://mbworld.org/forums/sl-class-r129/171567-how-do-you-get-code-check-engine-light.html.

The diagnostic socket for the top controller is #10, for the roll bar it is #8. EDIT: roll bar is $7!

Ok, I messed around with the switch, down for 20 seconds, then up for 10, not not achieve anything there.

I then went and conencted an LED to the diagnostic port, on pin 8, which is the roll bar port, I recieved 10 pulses, which according to another document I downloaded is SRS.

So I guess the next logical step would be to inspect the SRS module, is there a pin in the diagnostic port for the SRS module?

I fat-fingered my post: the roll bar is #7, not #8. SRS airbag is #6. The ignition system is #8...

The code "10" you read on #8 indicates no communication between the fuel injection and ignition controllers...Not a problem to be concerned with but one you may want to investigate.

Ok, on pin 7 we are able to get a constant single pulse, which per this http://www.mercedesshop.com/shopforu...=1#post1347434 guide would indicate that the roll bar system is functioning correctly.

On pin 10 however, we were unable to get a pulse at all, just a constant light, on both the soft top botton, and the LED.

From memory, the power windows are also controlled by the soft top controller, and they are functioning perfectly, and you can hear the relays click when the bottons are pressed.....

Langer, on your car when the roll bar automatically deploys, a code 24 is set in the soft top controller. As long as that code is in the controller memory the top is inoperable. The code will automatically clear once you lower the roll bar, so getting the roll bar to lower is the key.

When you press the roll bar switch nothing happens...You checked the fuses, but did you look in the trunk? In particular you need to check a fuse that doesn't look like a fuse at all -- it's the strip of metal between a pair of terminals at the lower end of the box. That's the fuse for the hydraulic pump. If that checks-out, I would check the input to the controller from the roll bar manual control switch next...

Yep, the fuse for the hydrolic pump is fine, as are all the other fuses in the trunk.

I will go and re-check the connection from the switch to the controller, but I think that is fine...have already gone over it and made sure nothing was loose.

What has got me interested though is the fact that I could not get a code from the soft top pin in the socket, however all the other pins were fine, I could not reset the soft top controller either.

I have a 92 300sl. Still trying to locate the diagnostic port. I think I have a 16 pin from what I have read and searched on. I purchased a code reader from a guy who makes them but he says it is near the battery...but that is on the newer r129's. I don't see any type of connector that looks even close to it either by the battery or up in the engine compartment. Where was your port?

found the diagnostic port
 

I found it! It is located under a plastic cover on the passenger side next to the front strut up against the divider piece that separates the computers from the engine compartment