hier die DIY Anleitung fuer die Sparversion aus Ohrenstopfen fuer < 0.25 EURO, wollte ich Euch doch nicht vorenthalten, aus einem U.S. E34 Forum
Hey guys, I actually fixed mine (functionally) for less than $0.25. The rubber on my key fob collapsed such that two of the buttons didn't work anymore. Figuring it was already "broke" I took it apart to see how it worked. Come to find that the convex (outer) part of the rubber button supports a little rubber shaft that pushed down on a smaller button affixed to the little circuit board. The problem with these being that as the convex part of the button deteriorates, it doesn't hold it's position and that shaft no longer presses against the circuit board when pressed. It literally goes sideways and sits there. (you'll see what I mean when you take yours apart.)
So, here's the quick, easy and cheap fix...
A foam ear plug. Yup. You can get a set of them at a hardware store for < $0.50 usually. This foam earplug material has a memory allowing you to compress them and stick them in your ear. Once in, they expand and make a good seal with your ear canal. See where I'm going with this? No? Then read on...
1)Get some scissors and and something round/thing to poke a hole (cut coat hanger works well).
2) Dissassemble your key fob
3) Assess which buttons need help.
4) Notice that the larger of the three buttons is just about the same circumference of the ear plug.
5) Measure that shaft on the inner part of the rubber button and cut a cross section from the ear plug just a bit longer than that. 1/16" longer is good.
6) Do the same for the smaller buttons, but you'll need to trim/shape their circumference down a bit to fit their cavity in the fob.
7) Once you have them all shaped, poke holes down the center of your foam for that shaft. It helps to remove a bit of material in the center if possible, but not so much that they won't hold that button shaft in place.
8) place your foam cut-outs over each of the button shafts and position for assembly.
9) Squish all the foam inserts and assemble before they expand again.
10) Enjoy your working key!
It still may look terrible, but it works now.