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1995 E320 Roll Bar Stuck in Up Position

10803 Views 5 Replies 5 Participants Last post by  Bernie2000
I have a 1995 E320 Cabriolet and the roll bars went up and stayed there after going over a speed bump. The roll bar functioned normally before this event and I was able to raise and lower the bar via the normal specified function right up until the event with the bump. I have followed the discussion threads about this problem in as many places I can find and have checked out each suggestion that I could from the available information provided:

1. Performed the roll bar 'normal' activation/retraction sequence shown in the Owner's manual exactly as stated. I hear a mechanical noise after holding the Up rocker switch for the requisite period of time, but the roll bar will not drop when the switch is activated for Down.

2. The sensors on the rear axle were checked on both sides, were not damaged, found to be in the Function position, but were turned via the screw driver slot to the Arrested position and back to the Function position.

3. There were no Trouble Codes, and the Trouble Codes clearance process was done anyway.

4. All fuses were checked and found to be in working order.

I took the rear seat back off to see if there is some evident release mechanism. From what I can see there are two mechanisms on the roll bar - one hydraulic system and one separate dual-spring system. As I can figure it out, when a roll-over condition is detected there is a device that disconnects the hydraulic system from the roll bar (there is a good photo of this separation on another thread) and the roll bar is pushed upwards by the springs where it is locked in place. Looking down the spring towers on each side I see a long rack of metal teeth or dogs; I am assuming these dogs engage in a locking configuration to mechanically secure the roll bar in place when the roll over sensor is tripped.

I have seen videos on YouTube where they slip a tool down the side of a raised head rest (on another model) to release the locking mechanism. I am assuming you can do the same for the Cabriolet model. I tried slipping a hack saw blade down across the rack to feel if there is a way to release this lock up but the blade may not be long enough. I am assuming you will have to insert a tool on both sides at once as the roll bar locks up on both sides.

I think I have checked out all the suggestions that have appeared on the various threads. It makes sense that when a roll-over condition is sensed the hydraulic system is cut out and the roll bar is raised and locked into the Up position purely by the springs. As Mercedes has engineered a method to release this lock up on another model it would make sense that there is a way to unlock the roll bar in this model too.

As I stated, the roll bar up/down was working normally prior to the speed bump. There is no evidence of any fluid leakage on any of the components as I have taken the back seats off to inspect the entire hydraulic system.

Thank you for your thoughts.
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Captain -

Clark is correct that if the roll bar was deployed by the roll bar controller, a code will be set (Code 17), but strangely, this code cannot be read on via the Roll Bar diagnostic code readout on pin 9 of the Diag connector. Instead, it must be read via the soft stop controller whose diagnostic connector is not on the 16 pin under the hood, but rather located on a separate 4 pin connector in the passenger foot well. When you say the Trouble Codes were read, from where were they read? I have attached the code list and test locations for both the roll bar controller and the soft top controller.

If the roll bar deployed because of a mechanical issue (the spring loaded latches released), a code will not be stored as the roll bar has no separate sensor to indicate the roll bar is in the deployed state. This is a "calculated" code only. A bit of a design problem if you ask me, but it did save MB a sensor. If the roll bar deployed because of a mechanical issue, this could be a very hazardous condition as the roll bar could deploy at random times and perhaps injure someone. This is why it is important to determine if a code was really stored.

As for resetting the roll bar, I would suggest the following:

Check the fuses in the auxiliary fuses holder located on the right strut mount. The fuse that powers the roll bar deployment solenoid is located there.

Disconnect the battery for ~20 minutes to reset the codes in both the soft top controller and the roll bar controller (after you have read them).

Perform the roll bar reset procedure per the manual. If that does not work, try it again, but have an assistant press down on the roll bar while doing it - the latch may not be quite reaching the ratchet.

I have attached the service manual section the described roll bar operation in case the helps.

- FD


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