Door Locks and Head Rest Problems
 

Hi All,

Happy New Years! Just wanted to see if anyone can help me with this problem:

When unarming (unlocking) my W140 (s500) coupe, my right door lock does not unlock. It stays down even if I press the unlock button in the car. Also, the swtich that activates the head rest on the right rear does not work either. Please help!

Thanks so much

David

Others know way more than me, but my guess is that you have a vacuum leak somewhere in those two lines.

Thanks
 

But I don't know how to detect or fix a hose leak. Do you think its a DIY? Thanks

sounds like the PSE pump under the rear seat. a easy way to check if the pump is working is to swap the left and right door hose and see if your right doow unlock while left remain locked. If it does, it means your pump have failed. If no difference, it means your pump is working and the hose is leaking....

I would also disconnect the pump to reset it. Re-connect power connection after 1 minute and see if there are any difference.

David,
I agree with the others on the right door lock.. sounds like a vacuum issue. In addition to possibilities already mentioned, could be the vacuum actuator in the door.
On the rear head rest, I think it depends on the year.... my '96 W140 Coupe rear head rests are electrically driven, not vacuum. Believe early years were vacuum driven.
Does the head rest go up and down with the console mounted switch? Is it just the switch in the rear console that doesn't work?

Lock
 

It sounds like the actuator or the lines (hoses) going to it. The pump does not lock /unlock individual doors, they all get same vacuum/pressure. The high line cars had electric headrests the others had vacuum, and those were controlled by the pump under the rear seat. For about $50 you can get a handheld tester which produces pressure and vacum with a guage to indicate leaks

where is the door actuator located and how to replace it?

the problem i had was when i turned key in drivers door it unlocked but it does not unlock all the doors,if i turn the key to unlock the central locking system in the passengers doors,all locks unlock and lock,except for the drivers side,it was found to have a defective electrical/vacum actuator,your head rests may just have a defective switch.always assume the easiest fix and diagnose from there.