Rear Head Restraints Won't Drop on Mercedes W124?

Question

Hello
On my 1987 W124 200D (European Edition), the rear head-restraints do not drop anymore by pushing the button on central console. I have checked the relay under the floor behind the driver seat and it is working perfectly. There might be a problem with the vaccum supply. For the time being I have made them drop by pulling the the pneumatic actuators in the trunk under the head-rests but I would like to restore the original functionality.

How can I solve this problem?

Thanks for your help.

Thank you Wingless Pilot for informative answer. Actually I have already checked that the switch is working fine because the pneumatic release valve (relay) is triggered when you press the switch. However, I can't "feel" any vacuum in the supply line across the valve. I wish I had MityVac so that I could induce vacuum externally to see whether it is really a vacuum leak issue.

I have no clear idea on how to check the vacuum lines for leaks. Could you give me a hint on this?

Answer 1

You might want to check the pneumatic line line that runs all the way to the head-rest unit actuator/release points; check for leaks/obstructions...those vaccum lines can be problematic if leaks occur. Also check the switch at the dashboard level, make sure it is getting its "command" (when you press it a signal goes out for the actuators to do their thing). Can't rule-out the chance that the switch doesn't do anything more than move with a clicking sound due to ageing or some time/usage-induced defect.

Answer 2

i have the same car (im in the us and have a 260 though) if i were you off to my dealer i would go