(I'm re-posting this, as it appears the original got wiped out in the Sept server crash. It's not as complete as the original post, but I think better than nothing)
I'll assume you've tried the contact cleaner sprayed into the switch on the car fix and it either didn't help, or was short-lived.

Firstly, here's a good reference with pictures on doing this job on the same switch that is used in the Range Rover. http://www.rangerovers.net/repairdetails/seatcontrols.htm The idea is to disassemble the switch, clean the contacts, and re-assemble, so without going into detail on removing the switch fron the door (which varies according to model/year), here are some pointers. (All work was done on my 1985 380SE passenger side switch BTW)

- All work is easier if the lower half of the switch case is kept level and steady, so start by screwing the switch case to a piece of wood. You can use the 2 mounting screws, or shorter sheet metal screws.

- I borrowed the wife's cookie baking pan, which is large, flat, (the pan that is) and has raised edges to catch stray parts. I also lined the bottom with paper towel to make it easier to see things, prevent them bouncing.

- Work the little plastic clips around the circumference by inserting small 'wedges to keep the sides of the lower case half out a bit from the clips. I used small flat blade screwdrivers and bits. There were 7 clips on mine. I found that when the clips/pins on 2 adjacent sides are pryed apart, the cover comes right out, straight up. When it did, all the little balls were still sitting on their posts.

Note: First time, it's nice to have everything stay together when the cover comes off (pic 2 was shot right after the cover was removed), but I'd just dive in now and put it all back together later. It's a very simple mechanism. The little wing shaped contact bars are pushed down on the lower contact spots, which look like old-time ignition points, when the spring-loaded balls are squeezed down by the shape of the lower and upper case halves. The corrosion that covers the contacts and the bars prevents current flow and that is why your switch fails. The fix is to remove the bars and clean them and the points.

- All but the main moving piece can be removed and the little bars cleaned with fine paper, say 600 grit, with or without spray contact cleaner, same for the contact points on the lower case half. You can also swap the bars around to move a high-use pair to a lesser used part (like the headrest pair to the main).

- Re-assembly is just as easy. Simply reinsert the bars and replace the springs and top balls (and any lower balls that you might have dropped if you inverted the lower case). This is where that piece of wood does its stuff, keeping the assembly steady so none of the balls fall off as you carefully reinsert the case cover and engage those tabs.

This is an easy and satisfying job BTW, and anyone with a reasonably steady hand can do it.

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1986 560SL
2002 Toyota Camry
1993 Lexus