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.