Pulling down the rear head rests in a benz is normally partly electrical and partly vacuum controlled. If you want to change that into a remote putting-them-up system, you probably have to change the complete system...I have never seen the remote up system, but I can imagine that it is electrical controlled (it is hard to believe that mercedes has a feature to pop up the rear head rests with the normal vacuum pods that are used in almost all the models.

...don't know anything about the W140...greetingz,

__________________
1990 300SL-24
1993 C250D with a minor 600+k kilometer
www.MBenzNL.com(the Netherlands)