W124 - Rear headrest drop not working
 

My rear headrests don't fold down at all. I only get a small click back there when I press the button. I'm guessing some kind of vacuum issue? Where are the lines to check?

dont know about how to diagnose this, but my rear headrests are a hit and miss thing, if i jiggle them sometimes (like i am raising them) and then press the release switch, they will fall. also, other times i have held down the switch for like two minutes and then they fell...

Did you try dropping them with the engine on?

http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=124133%5F15S&M=603%2E960&GA=722%2E357&CT=F&cat=15S&SID=80&SGR=150&SGN=07

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Yes, I did. Same result.

look at the diagram in my other post.
 

ur gonna have ta pull the back seat bottom and trouble shoot it from after the vacuum solenoid valve (the hose running from the valve to the head rests). Apply some vac and see if they fall. If they do then it is a vacuum or solenoid valve issue(check that the vavle is getting current). In that case you'll have to do a search on a rebuild or hit a bone yard. If they don't fall, you'll have to trace the line to the actuators and check it for leaks. If that anit it test each head rest indiviually. (you have to go through the trunk to access the head rests under the package shelf). There is a button on top of each actuator. Press it and the head rest will fall. (watch your fingers;)

I'd bet anything it's the solenoid under the back seat. It's in a bad location and any moisture that could possibly collect there will corrode it.

i have same problem-
 

I am having same problem with my w124, i unplugged them out back by the trunk and applied vacuum and they dropped but i have tried more than one selenoid and i still cant get them to work.
Any ideas?

Does the solenoid click when the button is pressed / key on?

If no, wiring or switch. If yes, there's a vacuum leak. This vacuum is generated by the engine vac-pump, so the engine must be running.

No clicks.

Check the switch next I guess.

And all of the fuses for dirty-marginal electrical contacts.

I now have a new selenoid and a new switch, i do hear a single click and thats it, i dont see headrests dropping or feel any vacuum coming or going, i even unplugged vac lines as to feel for vacuum but nada.

The vacuum comes from the running engine, through the same vacuum line that feeds the clmate-control IIRC. Are the climate control flaps operating properly?