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Hello.

I've got a W124 Cabrio with tombstone rear headrests that keep popping up as I'm driving along. I don't know why this happens: has anyone got any ideas why they've started doing this?

Thanks.
 

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1989 500SL (R129);2001 R170 230SLK; 1992 320CE
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1,036 Posts
Hello.

I've got a W124 Cabrio with tombstone rear headrests that keep popping up as I'm driving along. I don't know why this happens: has anyone got any ideas why they've started doing this?

Thanks.
Must be an issue with the sensor that measures the likelihood that the car is going to turn-over.
 

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94 S500, 99 G320, 99 C280 Sport
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1,151 Posts
Very expensive situation to diagnose. I changed the sensors on the rear control arms ($200), it didn't help. Changed the control unit that sits under the rear seat, didn't help ($2000).
Finally gave up and had the bolted down until I can come up with a different solution ($30).
Please keep this thread updated if you find a solution.
 

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1999 C280
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898 Posts
Would be interested to see if anyone else has additional info. On my car, maybe 1x per month or 2, my drivers side headrest will raise itself up. I just put it down and forget about it til it rises again.
 

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R129 SL500 (98,97,95,92), W124 (E500&320 93Cabriolet)R107,Toyota Landcruiser2010, Nissan Murano2015,
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229 Posts
How to test, adjust and replace your head rest/roll bar sensors

Hello.

I've got a W124 Cabrio with tombstone rear headrests that keep popping up as I'm driving along. I don't know why this happens: has anyone got any ideas why they've started doing this?

Thanks.
Hi guys,

You problem is vey simple, all what you have to do is follow the below steps for testing and replacing/adjusting the sensor:

- Testing the roll bar sensor:


Set rotating part (1) on one of the two rear axle switches to "arrested".

Then drive the vehicle to test. The roll-over bar should extend (crash actuation) when the vehicle is braked sharply from a speed of approx. 5-10 km/h . After testing set the rotating part (1) back to "Function".

NOTE: A clicking noise is audible as the roll-over bar extends.


- Replacing the roll bar sensor:

Removal

Roll-over bar
put up with convenience switch
Ignition
switch off
Negative pole on battery
disconnect and cover
Connector for rear axle switch on left (S3/2x) and right (S83/3x)
release by pressing (arrow)
Connectors
disconnect
Nuts (2)
loosen
Rear axle switches (S83/2,S83/3)
remove
Nuts (2)
retighten (4 + 0.5 Nm )

Installation

NOTE: The rear wheels must hang freely (rear axle suspension extended completely)

Rotating part (1) on both rear axle switches
turn to arrested position.
Nuts (2)
unscrew
Rear axle switches on left and right
position on bolts. Tighten nuts (2) hand-tight.
Rear axle switches
grip with hand on lever and position tip (3) against covering (4).
Nuts (2)
tighten (4 + 0.5 Nm ).
Function of roll-over bar
check.
Roll-over bar should actuate. (see the testing above)
Rotating part (1)
turn back to function position.

Hope the above information will help you to fix your problem.

Regards,
 

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