I have a 94 S500, and am having a problem with the power headrests on the rear seats. They work intermitantly from either the front or rear switches. You can hear the relays working back there, and sometimes
they both go up just like they should, other times one comes up and the other stays down,
and sometimes they both stay down. They generally go back down as they should.
I would guess it is a problem with the relays, but I don't know how to get to them to check them (thinking maybe I can get away with just cleaning the contacts) or replace them. Any guidance or help on how to fix these??
Thanks,
Barry

Hello bbrewer:

I'm having the same problem with my 94 E500 (is it the vintage?). I hope someone has some advice or suggestions.

I have same issue, traced all lines both vacumn and electrical and everything appears to function as planned, but still have problem.

Try this, I noticed mine work better when cold start in the morning. Vacumn lines are closed tighter than warm? I dont know.

Next time try revving up the engine 2000 rpm, then as revs fall press the headrest button.

Mine drop every time now. After spring comes I'll take a closer look as to where the leak is.

Good Luck

------------------
Mike Mullins
71 250 Coupe
92 400E Sedan
90 944/S2 Cabriolet

I thought only those on W140/W220 with electric rear seats has power rear headrests?? Those on W124s are mechanical, aren't they??

Thanks, Mike. I will give it a shot and let you know my findings.

Barry

It just turned cold around here, and as of yesterday, the headrests are working perfectly. No delays, no annoying "clicking", no taking turns "maybe" going up.
They both went up and down in unison, every time.
The RPMs didn't seem to matter, but it WAS cold (mid 40s), so maybe there IS something to your theory, Mike. It just seems that they should work better in warmer weather, not cold.
Oh well, more "study" is required here.

Thanks,

Barry

Well, after working with them more, it appears that the cold has a minimal affect, if any. It seems that the engine RPMs are much more important. When decelerating, they work pretty much every time. When sitting still idling, they only work sometimes. So, we obviously need to have the engine in a condition of high vacuum.
Now that I know their ideal state of operation, I have just decided that there is really nothing wrong with them other than marginal vacuum. So....I am going to fixate on something on another car.
I guess if rear power headrests are my only concern on the S500, this must be one heckuva car!!!<BG>
Thanks for your ideas and help!!

Barry

Just a follow-up.
I don't use the headrests much, but now I am getting a "ratcheting" sound for a few seconds AFTER they position themselves either up or down. Obviously something is breaking down and allowing too much play in the lifting mechanism. They still work, but the noise is embarrassing AND it's going to break, no doubt.
Any suggestions on what I am looking at here as far as a diagnosis, and how hard a job to repair for a reasonably competent do-it-yourselfer??
Again, the car is a 94 S500.

Thanks,

Barry

akry - the 126 is mechanical. So, we 126 owners could just enjoy this thread and think how lucky we are not to have this problem now, or in the future. :)

But I do hope that this problem can be solved ..

Best wishes from where we are.

Dean, MikeM,

As far as I know the european W124, the rear headrests do only have a remote pull down function. They have to be pulled up by hand.
Folding down the headrests is partial electrical and partial vacuum controlled. The vacuum comes from the engine and therefore the engine has to provide sufficient vacuum to fold the rear headrests. If you have to push the button for a longer while to get the headrests to fold down, you most probably have a small vacuum leak somewhere in the system (at least, that was what I had with my C class).
I never knew that the (W140) S class rear headrests could be put up again by button...is that partial vacuum controlled as well, or is that completely electrical?

greetingz,

For the W140, I believe them to be both electrical and vacuum operated, and that is for putting them both up and down.
But what is the ratcheting sound?? And how do I repair it??

Thanks,

Barry

Somewhat tangential, but I have a '97 S320 with the powered headrests in the rear and also the powered sun-screen for the rear glass. The latter is tremendously useful and I would be without it, but kindly clarify WTH I would care to have the headrests bouncing up and down? It is a complete mystery.....

Jerry,

If you have power read headrest, then you have rear power seat(s) as well. You can recline the rear seatback angle by using the switches on either side of rear doors. As for WHY headrests goes down/up, it improves rearward vision. With headrests up, it blocks about 30% of the rearward vision.

Bbrewer,

Have you get the problem resolved yet?? Please keep us with updated info!! :) Thnx...


Andy Kuo